Background: Vitamin K derivatives have an important role in bone formation and blood clotting. Vitamin K₂ [menaquinone-4 (MK-4)] is used for the treatment and prevention of osteoporosis. Recently, vitamin K was found to be effective for the prevention of osteoarthritis and may play a role in cartilage formation; however, the function of UBIAD1 (MK-4 biosynthesis enzyme) and MK-4 in cartilage is unclear. In this study, we examined the function of UBIAD1 and MK-4 in chondrogenesis and differentiation using chondrogenically differentiated cells. Methods: Mouse chondrocyte progenitor ATDC5 cells were used for siRNA knockdown of UBIAD1 to determine its effects on cell proliferation and chondrogenic differentiation. Proliferation and differentiation were assessed using the WST-8 assay and Alcian blue staining, respectively. The effects of MK-4 treatment and transfection of a human UBIAD1 expression plasmid on UBIAD1 knockdown cells were also examined. RESULTS: UBIAD1 knockdown significantly decreased the proliferation and chondrogenic differentiation of ATDC5 cells. MK-4 treatment suppressed ATDC5 cell proliferation and chondrogenic differentiation. It also affected UBIAD1 knockdown ATDC5 cells during chondrogenic differentiation. However, overexpression of human UBIAD1 promoted ATDC5 cell proliferation and chondrogenic differentiation and exhibited a similar effect on UBIAD1 knockdown ATDC5 cells. These results suggest that MK-4 has an inhibitory effect on the proliferation and differentiation of UBIAD1, which exhibits a promoting effect. These results suggest that UBIAD1 and MK-4 have a role in regulating chondrocyte proliferation and differentiation and are important regulators of chondrogenic differentiation.

Gummy drugs are dried jelly formulations prepared by adding a gelling agent to saccharides, which are then cooled and solidified. Epinastine hydrochloride (Epi) is commonly used to treat allergic diseases as a prescription and over-the-counter drug. However, the extremely bitter taste of Epi would affect its acceptability among patients. In this study, we aimed to improve the palatability of a gummy drug containing Epi (Epi-G) via organoleptic masking. Epi-G (10 mg of Epi/3.5 g of gummy drug) with two different organoleptic masking formulations, namely aspartame, cocoa powder, and chocolate flavoring (C-Epi-G) or aspartame, L-menthol, and lemon flavoring (L-Epi-G). The gustatory sensation test included six healthy adult volunteers (23.3 ± 1.8 years). We used a visual analogue scale (VAS) to evaluate bitterness, sweetness, and the overall palatability of each Epi-G formulation during chewing and after spitting out the drugs. In the gustatory sensation test, the VAS scores for bitterness and sweetness were decreased and increased for C-Epi-G and L-Epi-G, respectively, compared with the values for Epi-G without organoleptic masking. The VAS scores for overall palatability during chewing for C-Epi-G and L-Epi-G were significantly increased by 2.3- and 2.0-fold, respectively, versus the value for Epi-G. The score after spitting out C-Epi-G remained higher than that of Epi-G. These data illustrated that Epi-G with organoleptic masking had good palatability, which could improve patient adherence to treatment. The gummy drugs could represent an alternative dosing formulation for pediatric and geriatric patients by allowing them to take the drugs more easily than other oral formulations.

Xanthine oxidase (XO) produces reactive oxygen species (ROS) and has been associated with vascular endothelial dysfunction. While the effects of xanthine oxidoreductase (XOR) inhibitors on inhibiting the generation of uric acid from xanthine have been reported, much less is known about their effects on XO-induced ROS. The mechanisms of action of each XOR inhibitor vary, but it is not known whether XOR inhibitors’ effects on oxidative stress also vary. The purpose of this study is to compare the effects of different XOR inhibitors on XO-induced ROS. We used an in vitro chemiluminescence assay with clinically relevant doses of XOR inhibitors (allopurinol, oxypurinol, febuxostat, and topiroxostat) to investigate their effects on circulating XO-derived ROS. All XOR inhibitors significantly inhibited ROS production, with febuxostat and topiroxostat showing strong effects. These results confirm differences in the effects at clinical did among XOR inhibitors on XO, with topiroxostat demonstrating a strong suppression of ROS production. This study should help guide clinical practice in using XOR inhibitors to improve patient care and management.

EDEM2 plays an important role as the first enzyme that acts during mannose trimming of N-glycosylated proteins in the ERAD machinery. Although EDEM2 expression has been reported to be transcriptionally regulated by the IRE1-sXBP1 pathway, very little is known about how endogenous EDEM2 protein expression is regulated. In this work, three different ER stress inducers were used to treat HEK293 cells. Thapsigargan slightly increased both EDEM2 mRNA and protein levels in the cells. Treatment with MG132 did not increase the level of mature EDEM2 protein, and a truncated form of the protein appeared. In SEL1L-deficient cells, there was a slight increase in EDEM2 protein as well as in TXNDC11, a protein that has been reported to form disulfide bonds with EDEM2. On the other hand, EDEM2 protein level decreased in TXNDC11-deficient cells. DTT treatment decreased EDEM2 and TXNDC11 protein levels in a time-dependent manner. The decrease in EDEM2 protein after DTT treatment was attenuated by treatment of the cells with MG132 and by SEL1L deficiency. These findings demonstrate that endogenous EDEM2 protein is regulated posttranscriptionally and that it is in part an SEL1L-mediated ERAD substrate.