ABSTRACT
The aim of the present study was to investigate the pathophysiological etiology of osteoarthritis that is mediated by the apoptosis of chondrocytes exposed to 25-hydroxycholesterol (25-HC), an oxysterol synthesized by the expression of cholesterol-25-hydroxylase (CH25H) under inflammatory conditions. Interleukin-1β induced the apoptosis of chondrocytes in a dose- dependent manner. Furthermore, the production of 25-HC increased in the chondrocytes treated with interleukin-1β through the expression of CH25H. 25-HC decreased the viability of chondrocytes. Chondrocytes with condensed nucleus and apoptotic populations increased by 25- HC. Moreover, the activity and expression of caspase-3 were increased by the death ligand-mediated extrinsic and mitochondria-dependent intrinsic apoptotic pathways in the chondrocytes treated with 25-HC. Finally, 25-HC induced not only caspasedependent apoptosis, but also induced proteoglycan loss in articular cartilage ex vivo cultured rat knee joints. These data indicate that 25-HC may act as a metabolic pathophysiological factor in osteoarthritis that is mediated by progressive chondrocyte death in the articular cartilage with inflammatory condition.
ABSTRACT
The aim of the present study was to investigate the pathophysiological etiology of osteoarthritis that is mediated by the apoptosis of chondrocytes exposed to 25-hydroxycholesterol (25-HC), an oxysterol synthesized by the expression of cholesterol-25-hydroxylase (CH25H) under inflammatory conditions. Interleukin-1β induced the apoptosis of chondrocytes in a dose- dependent manner. Furthermore, the production of 25-HC increased in the chondrocytes treated with interleukin-1β through the expression of CH25H. 25-HC decreased the viability of chondrocytes. Chondrocytes with condensed nucleus and apoptotic populations increased by 25- HC. Moreover, the activity and expression of caspase-3 were increased by the death ligand-mediated extrinsic and mitochondria-dependent intrinsic apoptotic pathways in the chondrocytes treated with 25-HC. Finally, 25-HC induced not only caspasedependent apoptosis, but also induced proteoglycan loss in articular cartilage ex vivo cultured rat knee joints. These data indicate that 25-HC may act as a metabolic pathophysiological factor in osteoarthritis that is mediated by progressive chondrocyte death in the articular cartilage with inflammatory condition.
ABSTRACT
BACKGROUND: This study was designed to evaluate the effect of monaural headset to the hearing threshold shifts of the female communication workers. METHODS: Hearing threshold shifts of total 642 subjects, selected after excluding workers with history of ear disease, of ototoxic drug administration, and of neuropsychiatric disease, were determined by pure tone audiometric tests. Each worker's personal and work history was taken by the self-administrative questionnaire. In addition, occupational noise exposure levels in the workplace were assessed by noise dosimetry and each worker's noise exposure from the headset was measured by placing the microphone of a noise dosimeter to the external portion of the headset which was coupled by a silicon tube. The hearing threshold shifts were compared between groups of the alternate and the fixed headset user. RESULTS: The results were as follows: 1> The noise levels in the workplace ranged from 62.1 dBA to 63.9 dBA. The mean equivalent sound levels (LEQ) by the headset volume (minimum, middle, and maximum) were 90.8 dBA, 94.6 dBA, and 97.8 dBA, respectively. The maximum sound level (Lmax) of the headset was from 109.1 to 128.6 dBA. 2> The degree of hearing difference of the one side users was higher than that of the alternate users. Comparing the hearing loss of two groups of subjects, hearing loss was statistically significantly higher in the left-ear fixed and in the alternate headset users with more than 15 years than those with less than 15 years of headset taking duration. 3> Based on the hearing loss evaluation criteria by the Korean Ministry of Labor, 25 required follow-up cases (3.89%) and 16 suspected cases (2.49%) out of the 642 subjects were screened. Although statistically not significant, the required follow-up cases were higher among fixed users (4.3%) than those of alternate users (3.7%). CONCLUSION: The results of this study ascertained the possibility of hearing loss due to monaural-headsets among female workers. Thus, it is recommended that an effective hearing conservation program should be provided for the headset-wearing communication workers.