Impaired osteoclastogenesis by staphylococcal lipoteichoic acid through Toll-like receptor 2 with partial involvement of MyD88

Yang, Jihyun,Ryu, Young Hee,Yun, Cheol-Heui,Han, Seung Hyun Wiley (John WileySons) 2009 Journal of leukocyte biology Vol.86 No.4

<P>Degenerative bone disease, marked by excessive loss of calcified matrix, is often associated with bacterial infections. Osteoclasts, which mediate the bone-resorptive process, are derived mainly from myeloid precursor cells of the monocyte/macrophage lineage, from which cells with phagocytic and inflammatory capacities may alternatively arise. Here, we investigated the effect of LTA, a major cell-wall virulence factor of Gram-positive bacteria, on osteoclast differentiation. Osteoclast precursors were prepared from C57BL/6 mouse BM using M-CSF and RANKL. When osteoclastogenesis was induced in the presence of staphylococcal LTA, LTA dose-dependently inhibited the differentiation of osteoclast precursors to mature osteoclasts. A corresponding inhibition of bone-resorptive function was observed in the reduced resorption area on calcium phosphate-coated culture plates. In contrast, the phagocytic and inflammatory potential of the osteoclast precursors increased in the presence of LTA. TLR2, known to recognize LTA, might be essential for the LTA inhibition of osteoclastogenesis, as the inhibition did not occur in the precursors from TLR2-deficient mice. Importantly, MyD88-dependent and MyD88-independent pathways would participate in the inhibition, as determined using MyD88-deficient cells. Moreover, LTA inhibited phosphorylation of ERK and JNK in osteoclast precursors stimulated with M-CSF and RANKL, concomitantly with a decreased DNA-binding activity of AP-1. These results suggest that staphylococcal LTA inhibits osteoclast differentiation primarily through TLR2 but also in part through MyD88 signaling, which in turn, inhibits activation of ERK, JNK, and AP-1.</P>

Risk factors and outcomes of acute renal infarction

( Jihyun Yang ),( Jun Yong Lee ),( Young Ju Na ),( Sung Yoon Lim ),( Myung Gyu Kim ),( Sang Kyung Jo ),( Wonyong Cho ) 대한신장학회 2016 Kidney Research and Clinical Practice Vol.35 No.2

Background: Renal infarction (RI) is an uncommon disease that is difficult to diagnose. As little is known about clinical characteristics of this disease, we investigated its underlying risk factors and outcomes. Methods: We performed a retrospective single-center study of 89 patients newly diagnosed with acute RI between January 2002 and March 2015 using imaging modalities. Clinical features, possible etiologies, and long-term renal outcome data were reviewed. Results: The patients`` mean age was 63.5 ± 15.42 years; 23.6% had diabetes and 56.2% had hypertension. Unilateral and bilateral involvements were shown in 80.9% and 19.1% of patients, respectively; proteinuria and hematuria were reported in 40.4% and 41.6%, respectively. Cardiovascular disease was the most common underlying disease, followed by renal vascular injury and hypercoagulability disorder. Fourteen patients had no specific underlying disease. At the time of diagnosis, acute kidney injury (AKI) was found in 34.8% of patients. Univariate analysis revealed diabetes mellitus (DM), leukocytosis, and high C-reactive protein (CRP) as significant risk factors for the development of AKI. On multivariate analysis, DM and high CRP levels were independent predictors for AKI. During follow-up, chronic kidney disease developed in 27.4% of patients. Univariate and multivariate Cox regression analyses showed old age to be an independent risk factor for this disease, whereas AKI history was a negative risk factor. Conclusion: DM patients or those with high CRP levels should be observed for renal function deterioration. Clinicians should also monitor for RI in elderly patients.

1.5 MeV electron irradiation damage in β-Ga₂O₃ vertical rectifiers

Yang, Jiancheng,Ren, Fan,Pearton, Stephen J.,Yang, Gwangseok,Kim, Jihyun,Kuramata, Akito American Institute of Physics 2017 Journal of Vacuum Science & Technology. B Vol.35 No.3

Probiotics partially attenuate the severity of acute kidney injury through an immunomodulatory effect

( Jihyun Yang ),( Geun Eog Ji ),( Myeong Soo Park ),( Yeong-je Seong ),( Yoon Sook Go ),( Hee Young Lee ),( Yina Fang ),( Myung-gyu Kim ),( Se Won Oh ),( Won Yong Cho ),( Sang-kyung Jo ) 대한신장학회 2021 Kidney Research and Clinical Practice Vol.40 No.4

Background: A healthy microbiome helps maintain the gut barrier and mucosal immune tolerance. Previously, we demonstrated that acute kidney injury (AKI) provoked dysbiosis, gut inflammation, and increased permeability. Here, we investigated the renoprotective effects of the probiotic Bifidobacterium bifidum BGN4 and the underlying mechanisms thereof. Methods: C57BL/6 mice were subjected to bilateral renal ischemia-reperfusion injury (IRI) or sham operation. In the probiotic-treated group, BGN4 was administered by gavage once daily, starting 2 weeks before injury. Results: Administration of BGN4 significantly increased gut microbiome diversity and prevented expansion of the Enterobacteriaceae and Bacteroidetes that were the hallmarks of AKI-induced dysbiosis. Further, BGN4 administration also significantly reduced other IRI-induced changes in the colon microenvironment, including effects on permeability, apoptosis of colon epithelial cells, and neutrophil and proinflammatory macrophage infiltration. Mononuclear cells co-cultured with BGN4 expressed significantly increased proportions of CD103⁺/ CD11c⁺ and CD4⁺ CD25⁺ Treg cells, suggesting a direct immunomodulatory effect. BGN4 induced Treg expansion in colon, mesenteric lymph nodes (MNL), and kidney. BGN4 also reduced CX₃CR₁^intermediateLy6C^high monocyte infiltration and interleukin (IL)-17A suppression in the small intestine, which may have attenuated AKI severity, kidney IL-6 messenger RNA expression, and AKI-induced liver injury. Conclusion: Prior supplementation with BGN4 significantly attenuated the severity of IRI and secondary liver injury. This renoprotective effect was associated with increased Foxp3 and reduced IL-17A expression in the colon, MNL, and kidney, suggesting that BGN4-induced immunomodulation might contribute to its renoprotective effects. Probiotics may therefore be a promising strategy to reduce AKI severity and/or remote organ injury.

The 4–1BB ligand and 4–1BB expressed on osteoclast precursors enhance RANKL-induced osteoclastogenesis via bi-directional signaling

Yang, Jihyun,Park, Ok Jin,Lee, Yeon Ju,Jung, Hong-Moon,Woo, Kyung Mi,Choi, Youngnim WILEY-VCH Verlag 2008 European journal of immunology Vol.38 No.6

<P>The 4–1BB is a costimulatory molecule similar to the receptor activator of NF-&kgr;B ligand (RANKL), both of which are key factors for the differentiation of osteoclasts and are expressed mainly by activated T cells. The 4–1BB shares common signaling pathways with RANK, suggesting a potential role in osteoclastogenesis. In this study, the role of 4–1BB and 4–1BB ligand (4–1BBL) in osteoclastogenesis was investigated using 4–1BB<SUP>–/–</SUP> and 4–1BB<SUP>+/+</SUP> mice. Osteoclast precursors normally express 4–1BB and 4–1BBL after exposure to RANKL, which was confirmed by semi-quantitative RT-PCR and flow cytometry. The 4–1BB<SUP>–/– </SUP>mice had a slightly increased bone mass accompanied by a reduced osteoclastogenic ability of 4–1BB<SUP>–/–</SUP> bone marrow-derived macrophages (BMM) ex vivo. In addition, 4–1BB<SUP>–/–</SUP> BMM demonstrated hypophosphorylation of JNK and p38 and decreased induction of c-Fos in response to RANKL stimulation. Retroviral transduction of wild-type as well as partial-length 4–1BB, which lacks TNF receptor-associated factor 2-binding sites for signaling, restored the osteoclastogenic ability of 4–1BB<SUP>–/–</SUP> BMM. Furthermore, both recombinant 4–1BB and 4–1BBL enhanced RANKL-induced osteoclastogenesis by 4–1BB<SUP>+/+</SUP> BMM and the induction of c-Fos and NFATc1.Together, these results indicate that 4–1BBL and 4–1BB expressed on osteoclast precursors enhance RANKL-induced osteoclastogenesis via bi–directional signaling, findings that may delineate the complex nature of the 4–1BBL and 4–1BB interaction.</P><P>Supporting Information for this article is available at www.wiley-vch.de/contents/jc_2040/2008/37650_s.pdf</P>

Probing patterned defects on graphene using differential interference contrast observation (4 pages)

Yang, Gwangseok,Kim, Jihyun American Institute of Physics 2015 Applied Physics Letters Vol.106 No.8

Self-aligned growth of CdTe photodetectors using a graphene seed layer.

Yang, Gwangseok,Kim, Donghwan,Kim, Jihyun Optical Society of America 2015 Optics express Vol.23 No.19

<P>We demonstrate the self-aligned growth of CdTe photodetectors using graphene as a pre-defined seed layer. Defects were generated in the graphene prior to growth to act as CdTe nucleation sites. Self-aligned CdTe structures were grown selectively on the pre-defined graphene region. The electrical and optoelectrical properties of the photodetectors were systematically analyzed. Our CdTe devices displayed Ohmic behavior with a low sheet resistance of 1.24 ?? 10⁸ 곽/sq. Excellent photodetecting performances were achieved, including a high on-off ratio (~2.8), fast response time (10.4 s), and highly reproducible photoresponses. The fabrication method proposed here for these self-aligned device structures proves valuable for the development of next-generation graphene-semiconductor hybrid devices.</P>

Single CdTe microwire photodetectors grown by close-spaced sublimation method.

Yang, Gwangseok,Kim, Byung-Jae,Kim, Donghwan,Kim, Jihyun Optical Society of America 2014 Optics express Vol.22 No.16

<P>We demonstrate single CdTe microwire field-effect transistors (FETs) that are highly sensitive to ultraviolet (UV) light. Dense CdTe microwires were catalytically grown using a close-spaced sublimation system. Structural, morphological and transport properties in conjunction with the optoelectronic properties were systemically investigated. CdTe microwire FETs exhibited p-type behaviors with field-effect mobilities up to 1.1 10(-3) cm2 V(-1) s(-1). Optoelectronic properties of our CdTe microwire FETs were studied under dark and UV-illumination conditions, where photoresponse was highly dependent on the back-gate bias conditions. Our CdTe microwire FET-based photodetectors are promising for high-performance micro-optoelectronic applications.</P>

Flexible graphene-based chemical sensors on paper substrates

Yang, Gwangseok,Lee, Chongmin,Kim, Jihyun,Ren, Fan,Pearton, Stephen J. The Royal Society of Chemistry 2013 Physical chemistry chemical physics Vol.15 No.6

<P>Graphene-based, flexible NO<SUB>2</SUB> sensors on paper substrates exhibited an immediate response (32–39%) once exposed to 200 ppm NO<SUB>2</SUB> gas under a strain of 0.5%. Chemical vapor deposition-grown graphene with a supporting poly(methyl methacrylate) layer was transferred onto paper substrates, followed by formation of two electrodes using silver paste. Current–voltage characteristics and dynamic sensing response were obtained under both relaxed and strained conditions. We demonstrate a facile method without complex photo-lithography and high vacuum processes for fabricating graphene-based flexible NO<SUB>2</SUB> sensors on paper substrates with high sensing response.</P> <P>Graphic Abstract</P><P>We demonstrate a simple method for fabricating graphene-based flexible chemical sensors on paper substrates with high sensing response. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp43717a'> </P>

GaN-based light-emitting diodes on graphene-coated flexible substrates.

Yang, Gwangseok,Jung, Younghun,Cuervo, Camilo V?lez,Ren, Fan,Pearton, Stephen J,Kim, Jihyun Optical Society of America 2014 Optics express Vol.22 No.suppl3

<P>We demonstrate GaN-based thin light-emitting diodes (LEDs) on flexible polymer and paper substrates covered with chemical vapor deposited graphene as a transparent-conductive layer. Thin LEDs were fabricated by lifting the sapphire substrate off by Excimer laser heating, followed by transfer of the LEDs to the flexible substrates. These substrates were coated with tri-layer graphene by a wet transfer method. Optical and electrical properties of thin laser lift-offed LEDs on the flexible substrates were characterized under both relaxed and strained conditions. The graphene on paper substrates remained conducting when the graphene/paper structure was folded. The high transmittance, low sheet resistance and high failure strain of the graphene make it an ideal candidate as the transparent and conductive layer in flexible optoelectronics.</P>