Yun Sil Lee

Mitochondrial components have been abundantly detected in bone matrix, implying that they are somehow transported extracellularly to regulate osteogenesis. Here, we demonstrate that mitochondria and mitochondrial-derived vesicles (MDVs) are secreted from mature osteoblasts to promote differentiation of osteoprogenitors. We show that osteogenic induction stimulates mitochondrial fragmentation, donut formation, and secretion of mitochondria through CD38/cADPR signaling. Enhancing mitochondrial fis

Expression of heat shock proteins (HSPs) has been shown to protect mammalian cells exposed to a variety of stress stimuli. Among various HSPs, small HSPs from diverse species were shown to protect cells against oxidative stress. Here, we show that the overexpression of the mouse small hsp gene, hsp25, provides protection against ionizing radiation. Our results demonstrate that the radiation survival of the L929 cells stably transfected with hsp25 was enhanced compared with that of the parental o

Park, S-H., Lee, S-J., Chung, H-Y., Kim, T-H., Cho, C-K., Yoo, S-Y. and Lee, Y-S. Inducible Heat-Shock Protein 70 Is Involved in the Radioadaptive Response. The thermoresistant (TR) clone of radiation-induced fibrosarcoma (RIF) cells showed an adaptive response, i.e. a reduced effect, after exposure to a higher challenging dose (4 Gy) when the priming dose (1 cGy) was given 4 or 7 h earlier, but RIF cells did not. Since inducible Hsp70 expression was different in cells of these two cell lines, t

Epidermal keratinocyte differentiation is a tightly regulated, stepwise process that requires protein kinase C (PKC) activation. Studies using cultured mouse keratinocytes induced to differentiate with Ca2+ have indirectly implicated the alpha isoform of PKC in upregulation of "late" (granular cell) epidermal differentiation markers. Activation of this isoform is also implicated in the suppression of "early" differentiation markers keratin (K) 1 and 10 that characterizes the neoplastic phenotype

Intracellular signaling molecules and apoptotic factors seem to play an important role in determining the radiation response of tumor cells. However, the basis for the link between signaling pathway and apoptotic cell death machinery after ionizing irradiation remains still largely unclear. In this study, we showed that c-Abl-PKCdelta-Rac1-p38 MAPK signaling is required for the conformational changes of Bak and Bax during ionizing radiation-induced apoptotic cell death in human non-small cell lu

Significance MSTN, a member of the TGF-β family, has been widely shown to suppress muscle growth, leading to an intense effort being directed at targeting MSTN to treat patients with muscle loss. GDF11 is another TGF-β family member closely related to MSTN, but its postnatal function is less clear. Using conditional knockout techniques, we show that GDF11 enhances bone mass in contrast to MSTN, emphasizing that MSTN/GDF11 inhibitors, such as FST, can induce adverse effects on bone through GDF11

We examined the histological changes by radiofrequency (RF) fields on rat testis, specifically with respect to sensitive processes such as spermatogenesis. Male rats were exposed to 848.5 MHz RF for 12 weeks. The RF exposure schedule consisted of two 45-min RF exposure periods, separated by a 15-min interval. The whole-body average specific absorption rate (SAR) of RF was 2.0 W/kg. We then investigated correlates of testicular function such as sperm counts in the cauda epididymis, malondialdehyd

Mitochondria have been primarily considered intracellular organelles that are responsible for generating energy for cell survival. However, accumulating evidence suggests that mitochondria are secreted into the extracellular space under physiological and pathological conditions, and these secreted mitochondria play diverse roles by regulating metabolism, the immune response, or the differentiation/maturation in target cells. Furthermore, increasing amount of research shows the therapeutic effect

Sprague-Dawley rats (10 each of male and female per group for sham and magnetic field exposed) were exposed in a carrousel irradiator to 20 kHz intermediate frequency (IF) magnetic field at 6.25 microT rms for 8 h/day, 5 days/week for 90 days. Urine analysis (pH, serum glucose, protein, ketone bodies, RBC, WBC, bilirubin, urobilinogen, and specific gravity), blood analysis [WBC, RBC, hemoglobin, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemogl

Mitochondria in osteoblasts have been demonstrated to play multiple crucial functions in bone formation from intracellular adenosine triphosphate production to extracellular secretion of mitochondrial components. The present review explores the current knowledge about mitochondrial biology in osteoblasts, including mitochondrial biogenesis, bioenergetics, oxidative stress generation, and dynamic changes in morphology. Special attention is given to recent findings, including mitochondrial donut f

Thermoresistant (TR) clone of radiation-induced fibrosarcoma (RIF) cells have been reported to show adaptive response to 1 cGy of low dose radiation, and hsp25 and inducible hsp70 are involved in this process. In the present study, to further elucidate the mechanism of how hsp25 and inducible hsp70 regulate the adaptive response, hsp25 or inducible hsp70 overexpressed RIF cells were irradiated with 1 cGy and cell cycle was analyzed. Hsp25 or inducible hsp70 overexpressed cells as well as TR cell