Ceramide is unusually abundant in epidermal stratum corneum and is important for permeability barrier function. Ceramides in epidermis also comprise an unusual variety, including 2-hydroxy (a-hydroxy)-ceramide. Six mammalian ceramide synthase/longevity assurance homologue (CerS/LASS) family members have been identified as synthases responsible for ceramide (CER) production. We reveal here that of the six, CerS3/LASS3 mRNA is the most predominantly expressed in keratinocytes. Moreover, its expression is increased upon differentiation. CerS family members have known substrate specificities for fatty acylCoA chain length and saturation, yet their abilities to produce 2-hydroxy-CER have not been examined. In the present study, we demonstrate that all CerS members can produce 2-hydroxy-CER when overproduced in HEK 293T cells. Each produced a 2-hydroxy-CER with a chain length similar to that of the respective nonhydroxy-CER produced. In HeLa cells overproducing the FA 2-hydroxylase FA2H, knockdown of CerS2 resulted in a reduction in total long-chain 2-hydroxy-CERs, confirming enzyme substrate specificity for chain length. In vitro CerS assays confirmed the ability of CerS1 to utilize 2-hydroxy-stearoyl-CoA as a substrate. These results suggest that all CerS members can synthesize 2-hydroxy-CER with specificity for 2-hydroxy-fatty acylCoA chain length and that CerS3 may be important in CER and 2-hydroxy-CER synthesis in epidermis.-Mizutani, Y., A. Kihara, H. Chiba, H. Tojo, and Y. Igarashi. 2-Hydroxyceramide synthesis by ceramide synthase family: enzymatic basis for the preference of FA chain length. J. Lipid Res. 2008Res. . 49: 2356Res. -2364
Background
Singing in an indoor space may increase the risk of SARS-CoV-2 infection. We conducted a case-control study of karaoke-related COVID-19 outbreaks to reveal the risk factors for SARS-CoV-2 infection among individuals who participate in karaoke.
Methods
Cases were defined as people who enjoyed karaoke at a bar and who tested positive for SARS-CoV-2 by RT-PCR between May 16 and July 3, 2020. Controls were defined as people who enjoyed karaoke at the same bar during the same period as the cases and tested negative. Odds ratio (OR) and confidence interval (CI) were calculated. ORs were adjusted by variables with significantly high odds ratio (aOR).
Results
We identified 81 cases, the majority of whom were active elderly individuals (median age: 75 years). Six cases died (case fatality ratio: 7%). Among the cases, 68 (84%) were guests, 18 of whom had visited more than two karaoke bars. A genome analysis conducted in 30 cases showed six types of isolates within four single-nucleotide variations difference. The case-control study revealed that singing (aOR 11.0, 95% CI, 1.2-101.0), not wearing a mask (aOR 3.7, 95% CI 1.2-11.2) and time spent per visit (aOR 1.7, 95% CI 1.1-2.7) were associated with COVID-19 infection.
Conclusions
A karaoke-related COVID-19 outbreak that occurred in two different cities was confirmed by the results of genome analysis. Singing in less-ventilated, indoor and crowded environments increases the risk of acquiring SARS-CoV-2 infection. Wearing a mask and staying for only a short time can reduce the risk of infection during karaoke.
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