Seung-Hae Kwon

High-resolution three-photon biomedical imaging using doped ZnS nanocrystals

Three-photon excitation is a process that occurs when three photons are simultaneously absorbed within a luminophore for photo-excitation through virtual states. Although the imaging application of this process was proposed decades ago, three-photon biomedical imaging has not been realized yet owing to its intrinsic low quantum efficiency. We herein report on high-resolution in vitro and in vivo imaging by combining three-photon excitation of ZnS nanocrystals and visible emission from Mn(2+) dopants. The large three-photon cross-section of the nanocrystals enabled targeted cellular imaging under high spatial resolution, approaching the theoretical limit of three-photon excitation. Owing to the enhanced Stokes shift achieved through nanocrystal doping, the three-photon process was successfully applied to high-resolution in vivo tumour-targeted imaging. Furthermore, the biocompatibility of ZnS nanocrystals offers great potential for clinical applications of three-photon imaging.

Ischemia-induced changes in glucagon-like peptide-1 receptor and neuroprotective effect of its agonist, exendin-4, in experimental transient cerebral ischemia

Glucagon‐like peptide‐1 receptor (GLP‐1R) protects against neuronal damages in the brain. In the present study, ischemia‐induced changes in GLP‐1R immunoreactivity in the gerbil hippocampal CA1 region were evaluated after transient cerebral ischemia; in addition, the neuroprotective effect of the GLP‐1R agonist exendin‐4 (EX‐4) against ischemic damage was studied. GLP‐1R immunoreactivity and its protein levels in the ischemic CA1 region were highest at 1 day after ischemia/reperfusion (I/R). At 4 days after I/R, GLP‐1R immunoreactivity was hardly detected in CA1 pyramidal neurons, and its protein level was lowest. GLP‐1R protein level was increased again at 10 days after I/R, and GLP‐1R immunoreactivity was found in astrocytes and GABAergic interneurons. In addition, EX‐4 treatment attenuated ischemia‐induced hyperactivity, neuronal damage, and microglial activation in the ischemic CA1 region in a dose‐dependent manner. EX‐4 treatment also induced the elevation of GLP‐1R immunoreactivity and protein levels in the ischemic CA1 region. These results indicate that GLP‐1R is altered in the ischemic region after an ischemic insult and that EX‐4 protects against ischemia‐induced neuronal death possibly by increasing GLP‐1R expression and attenuating microglial activation against transient cerebral ischemic damage.

High-fat diet-induced obesity increases lymphangiogenesis and lymph node metastasis in the B16F10 melanoma allograft model: roles of adipocytes and M2-macrophages.

To examine the effects of high‐fat diet (HFD) on melanoma progression, HFD‐fed C57BL/6N mice were subcutaneously injected with syngeneic B16F10 melanoma cells. At 3 weeks post‐injection, the tumors were resected; the mice were then sacrificed at 2 weeks post‐resection. HFD stimulated melanoma growth and lymph node (LN) metastasis as well as tumor and LN lymphangiogenesis. Lipid vacuoles in the tumor and M2‐macrophage (MΦ)s in the adipose and tumor tissues were increased in HFD‐fed mice. CCL19 and CCL21 contents were higher in LNs than in tumors. HFD increased both CCL19 and CCL21 levels in LNs and CCR7 in tumors. Adipose tissue‐conditioned media (CM) from HFD‐fed mice enhanced lymphangiogenesis, and mature adipocyte (MA)/M2‐MΦ co‐culture CM markedly stimulated the tube formation of lymphatic endothelial cell (LEC)s and B16F10 migration. Monocyte migration was moderately stimulated by B16F10 or MA CM, but tremendously stimulated by B16F10/M2‐MΦ co‐culture CM, which was enhanced by MA/B16F10/M2‐MΦ co‐culture CM. The co‐culture results revealed that MAs increased CCL2, M‐CSF and CCR7 mRNAs in B16F10s; vascular endothelial growth factor (VEGF)‐D mRNA in M2‐MΦs; and CCL19, CCL21 and VEGF receptor (VEGFR)3 mRNA in LECs. M2‐MΦs increased CCL2, M‐CSF and VEGF‐A mRNAs in B16F10s, whereas B16F10s increased VEGF‐C mRNAs in M2‐MΦs and VEGFR3 mRNA in LECs. These results indicate that in HFD‐fed mice, MA‐induced CCL2 and M‐CSF in tumor cells increase M2‐MΦs in tumor; the crosstalk between tumor cells and M2‐MΦs further increases cytokines and angiogenic and lymphangiogenic factors. Additionally, MA‐stimulated CCL19, CCL21/CCR7 axis contributes to increased LN metastasis in HFD‐fed mice.

Comparison of neuroprotective effects of five major lipophilic diterpenoids from Danshen extract against experimentally induced transient cerebral ischemic damage

We observed neuroprotective effects of five major lipophilic diterpenes derived from Danshen (Radix Salvia miltiorrhiza) extract, such as cryptotanshinone (CTs), dihydrotanshinone I (DTsI), tanshinone I (TsI), tanshinone IIA (TsIIA) and tanshinone IIB (TsIIB), in the hippocampal CA1 region (CA1) against transient ischemic damage in gerbils. These diterpenes were administered 30min before ischemia-reperfusion and the animals were sacrificed 4days after ischemia-reperfusion. In the vehicle-treated-group, cresyl violet positive (CV(+)) cells and neuronal nuclei (NeuN)(+) neurons were significantly decreased in the CA1. However, in the TsI- and CTs-treated-ischemia-groups, CV(+) and NeuN(+) neurons were abundant in the CA1. In the other groups, the number of CV(+) and NeuN(+) neurons was less than the TsI- and CTs-treated-ischemia-groups. In addition, gliosis induced by ischemic damage was apparently blocked in the TsI- and CTs-treated-ischemia-groups. These results suggest that TsI and CTs among five major lipophilic diterpenes have strong potentials for neuroprotection against ischemic damage.

Novel drug combination for Mycobacterium abscessus disease therapy identified in a Drosophila infection model

OBJECTIVES Mycobacterium abscessus is known to be the most drug-resistant Mycobacterium and accounts for ∼80% of pulmonary infections caused by rapidly growing mycobacteria. This study reports a new Drosophila melanogaster-M. abscessus infection model that can be used as an in vivo efficacy model for anti-M. abscessus drug potency assessment. METHODS D. melanogaster were challenged with M. abscessus, and infected flies were fed with a fly medium containing tigecycline, clarithromycin, linezolid, clofazimine, moxifloxacin, amikacin, cefoxitin, dinitrobenzamide or metronidazole at different concentrations (0, 100 and 500 mg/L). The survival rates of infected flies were plotted and bacterial colonization/dissemination in fly bodies was monitored by cfu determination and green fluorescent protein epifluorescence. RESULTS The D. melanogaster-M. abscessus model enabled an assessment of the effectiveness of antibiotic treatment. Tigecycline was the best drug for extending the lifespan of M. abscessus-infected Drosophila, followed by clarithromycin and linezolid. Several different combinations of tigecycline, linezolid and clarithromycin were tested to determine the best combination. Tigecycline (25 mg/L) plus linezolid (500 mg/L) was the best drug combination and its efficacy was superior to conventional regimens, not only in prolonging infected fly survival but also against M. abscessus colonization and dissemination. CONCLUSIONS This D. melanogaster-M. abscessus infection/curing methodology may be useful for the rapid evaluation of potential drug candidates. In addition, new combinations using tigecycline and linezolid should be considered as possible next-generation combination therapies to be assessed in higher organisms.

Neuroprotective effect of a new synthetic aspirin-decursinol adduct in experimental animal models of ischemic stroke.

Stroke is the second leading cause of death. Experimental animal models of cerebral ischemia are widely used for researching mechanisms of ischemic damage and developing new drugs for the prevention and treatment of stroke. The present study aimed to comparatively investigate neuroprotective effects of aspirin (ASA), decursinol (DA) and new synthetic aspirin-decursinol adduct (ASA-DA) against transient focal and global cerebral ischemic damage. We found that treatment with 20 mg/kg, not 10 mg/kg, ASA-DA protected against ischemia-induced neuronal death after transient focal and global ischemic damage, and its neuroprotective effect was much better than that of ASA or DA alone. In addition, 20 mg/kg ASA-DA treatment reduced the ischemia-induced gliosis and maintained antioxidants levels in the corresponding injury regions. In brief, ASA-DA, a new synthetic drug, dramatically protected neurons from ischemic damage, and neuroprotective effects of ASA-DA may be closely related to the attenuation of ischemia-induced gliosis and maintenance of antioxidants.

Neuroprotective effects of tanshinone I from Danshen extract in a mouse model of hypoxia-ischemia

Hypoxia-ischemia leads to serious neuronal damage in some brain regions and is a strong risk factor for stroke. The aim of this study was to investigate the neuroprotective effect of tanshinone I (TsI) derived from Danshen (Radix Salvia miltiorrhiza root extract) against neuronal damage using a mouse model of cerebral hypoxia-ischemia. Brain infarction and neuronal damage were examined using 2,3,5-triphenyltetrazolium chloride (TTC) staining, hematoxylin and eosin histochemistry, and Fluoro-Jade B histofluorescence. Pre-treatment with TsI (10 mg/kg) was associated with a significant reduction in infarct volume 1 day after hypoxia-ischemia was induced. In addition, TsI protected against hypoxia-ischemia-induced neuronal death in the ipsilateral region. Our present findings suggest that TsI has strong potential for neuroprotection against hypoxic-ischemic damage. These results may be used in research into new anti-stroke medications.

Quantification of cellular uptake and in vivo tracking of transduction using real-time monitoring.

Protein transduction domains (PTDs) are short amino acid sequences that promote their own translocation across the cell plasma membrane and have been studied for possible use in drug delivery and gene therapy. However, no direct method to quantify transduction is available. Here, using a new luciferase-tagged human PTD, we show that cellular uptake levels can be determined in a reliable manner. Furthermore, we show that enhanced in vivo tracking by human PTD can be quantified in a mouse model. This is the first report on the direct quantification of PTD transduction in vitro and in vivo, which will be necessary for studying its possible therapeutic application in drug delivery and gene therapy.

Antidepressant-like effects of Cortex Mori Radicis extract via bidirectional phosphorylation of glucocorticoid receptors in the hippocampus

Excessive and prolonged secretion of adrenal glucocorticoids leads to a wide range of pathophysiological processes, including depression. Glucocorticoids, which act at glucocorticoid receptors (GR), are key regulators of the limbic hypothalamic-pituitary-adrenocortical (HPA) axis. In the present study, the antidepressant-like effects of the alcohol extract Cortex Mori Radicis (CMR) and its role in GR signalling were investigated. Male Wistar rats were administered CMR extract (50, 100, 200mg/kg, p.o.) daily for 5 days and then exposed to the forced swim test (FST). Behavioural analyses showed that CMR extract dose-dependently decreased immobility time during forced swimming. CMR extract also decreased the limbic HPA axis response to the FST, as indicated by an attenuated corticosterone response and decreased c-fos immunoreactivity in the dentate gyrus. Reduced hippocampal GR expression following exposure to the FST was reversed by CMR treatment. Moreover, a prominent increase in GR phosphorylation at S232 and a decrease at S246 were noted following treatment with CMR. This resulted in a high pGR(S232)/(S246) ratio. CMR treatment also produced a downregulation of serine/threonine protein phosphatase 5 levels, producing a strong negative relationship with pGR(S232). Taken together, our findings suggest that the alcohol extract CMR promotes antidepressant-like effects through bidirectional phosphorylation of GR at S232 and S246.

Human eye-inspired soft optoelectronic device using high-density MoS 2 -graphene curved image sensor array

Soft bioelectronic devices provide new opportunities for next-generation implantable devices owing to their soft mechanical nature that leads to minimal tissue damages and immune responses. However, a soft form of the implantable optoelectronic device for optical sensing and retinal stimulation has not been developed yet because of the bulkiness and rigidity of conventional imaging modules and their composing materials. Here, we describe a high-density and hemispherically curved image sensor array that leverages the atomically thin MoS2-graphene heterostructure and strain-releasing device designs. The hemispherically curved image sensor array exhibits infrared blindness and successfully acquires pixelated optical signals. We corroborate the validity of the proposed soft materials and ultrathin device designs through theoretical modeling and finite element analysis. Then, we propose the ultrathin hemispherically curved image sensor array as a promising imaging element in the soft retinal implant. The CurvIS array is applied as a human eye-inspired soft implantable optoelectronic device that can detect optical signals and apply programmed electrical stimulation to optic nerves with minimum mechanical side effects to the retina.Soft and flexible optoelectronic devices may provide effective routes toward retinal implants for enhanced visual functions. Here, the authors fabricate a curved array of flexible MoS2-graphene photodetectors and demonstrate its potential application as ophthalmic imaging element in mouse models.