Serology suggests adequate safety measures to protect healthcare workers from COVID-19 in Shiga Prefecture, Japan.

Healthcare workers (HCWs), especially frontline workers against coronavirus disease 2019 (COVID-19), are considered to be risky because of occupational exposure to infected patients. This study evaluated the correlation between seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies among HCWs and the implementation of personal protective equipment (PPE) & infection prevention and control (IPC). We recruited 1237 HCWs from nine public COVID-19-designated hospitals in Shiga Prefecture, central Japan, between 15-26 February 2021. All participants answered a self-administered questionnaire and provided blood samples to evaluate SARS-CoV-2 antibodies. A total of 22 cases (1·78%) were seropositive among the 1237 study participants. An unavoidable outbreak of SARS-CoV-2 had occurred at the terminal care unit of one hospital, before identifying and securely isolating this cluster of cases. Excluding with this cluster, 0·68% of HCWs were suspected to have had previous SARS-CoV-2 infections. Binomial logistic regression from individual questionnaires and seropositivity predicted a significant correlation with N95 mask implementation under aerosol conditions (p = 8.63e-06, aOR = 2.47) and work duration in a red zone (p = 2.61e-04, aOR = 1.99). The institutional questionnaire suggested that IPC education was correlated with reduced seropositivity at hospitals. Seroprevalence and questionnaire analyses among HCWs indicated that secure implementation of PPE and re-education of IPC are essential to prevent SARS-CoV-2 infection within healthcare facilities. Occupational infections from SARS-CoV-2 in healthcare settings could be prevented by adhering to adequate measures and appropriate use of PPE. With these measures securely implemented, HCWs should not be considered against as significantly risky or dirty by local communities.

Application of enzymatic fluorometric assays to quantify phosphatidylcholine, phosphatidylethanolamine and sphingomyelin in human plasma lipoproteins.

Phosphatidylcholine (PC), phosphatidylethanolamine (PE) and sphingomyelin (SM) are important surface components of plasma lipoproteins, including very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL) and high-density lipoproteins (HDL). However, the pathophysiological roles of PC, PE and SM in lipoproteins have not been well characterized owing to the difficulties in quantifying phospholipid classes in lipoproteins. In this study, we assessed the precision and accuracy of the enzymatic fluorometric assays for measuring PC, PE and SM in VLDL, LDL and HDL, which were isolated from human plasma by ultracentrifugation. The within-run coefficients of variation (CV) for the measurements of PC, PE and SM in lipoproteins were 1.5-2.8 %, 1.1-2.4 % and 0.9-2.3 %, respectively, whereas the between-run CVs for the PC, PE and SM assays were 2.7-4.7 %, 2.1-4.5 % and 1.6-3.3 %, respectively. Excellent linearity and almost complete recovery were achieved for all assays measuring PC, PE and SM in VLDL, LDL and HDL. Our preliminary results using these enzymatic fluorometric assays suggested that the phospholipid compositions were different among VLDL, LDL and HDL. In conclusion, we established high-throughput enzymatic fluorometric assays to quantify PC, PE and SM in human plasma VLDL, LDL and HDL, which will be useful for further investigation of pathophysiological roles of phospholipids in lipoproteins.

Transport Characteristics of 5-Aminosalicylic Acid Derivatives Conjugated with Amino Acids via Human H+-Coupled Oligopeptide Transporter PEPT1.

5-Aminosalicylic acid (5-ASA) is used as first line therapy for symptom remission and maintenance of inflammatory bowel disease (IBD). Because 5-ASA is well absorbed from the small intestine when orally administered, several 5-ASA formulations for selective delivery to the colon have been developed and used in clinical practice. However, its delivery efficiency to local inflamed colonic sites remains low. Intestinal H+-coupled oligopeptide transporter 1 (PEPT1) expression in the colon is low, whereas its expression is induced in the colon under chronic inflammation conditions, such as IBD. Therefore, we considered that PEPT1 would be a target transporter to improve 5-ASA delivery efficiency to local colonic lesions. We evaluated the transport characteristics of dipeptide-like 5-ASA derivatives, which were coupling glycine (Gly), lysine, glutamic acid (Glu), valine (Val) and tyrosine to amino or carboxyl group of 5-ASA, in Caco-2 cells. [3H]Glycylsarcosine (Gly-Sar) uptake into Caco-2 cells was inhibited by all 5-ASA derivatives. In addition, 5-ASA derivatives (Gly-ASA, Glu-ASA and Val-ASA), which were coupled by glycine, glutamic acid and valine to amino group of 5-ASA, were taken up in a pH- and concentration-dependent manner and their uptake was inhibited by excess Gly-Sar. Two-electrode voltage-clamp experiment using human PEPT1 expressing Xenopus oocytes showed that Gly-ASA, Glu-ASA and Val-ASA induced marked currents at pH 6.0. Taken together, these results showed that these 5-ASA derivatives are transportable substrates for PEPT1.

Transport characteristics of 5-aminosalicylic acid into colonic epithelium: Involvement of sodium-coupled monocarboxylate transporter SMCT1-mediated transport system.

5-Aminosalicylic acid (5-ASA) is conventionally used as a first line drug for inflammatory bowel disease (IBD). Because 5-ASA is well absorbed in the small intestine, very high dose of 5-ASA is required to deliver it to the large intestine which is a target site. Interestingly, 5-ASA is reported to be transported into the large intestine as well as the small intestine via unknown transport system. In a heterologous expression system using Xenopus oocytes, sodium-coupled monocarboxylate transporter 1 (SMCT1) has been reported to accept 5-ASA as a substrate. Although SMCT1 is found to be expressed in the large intestine, it is unknown whether SMCT1 is responsible for 5-ASA absorption from the large intestine or not. Here we determined the transport characteristics of 5-ASA in the isolated everted sac prepared from mouse large intestine. Na+-dependent uptake of [3H]nicotinate, a substrate for SMCT1, in mouse colon was competitively inhibited by 5-ASA with IC50 value of 2.8 mM. In addition to nicotinate, 5-ASA uptake in mouse colonic mucosa was Na+-dependent and saturable with Michaelis constant (Km) of 2.4 mM. Na+-activation kinetics revealed that the Na+-to-5-ASA stoichiometry was 2:1 and concentration of Na+ necessary for half-maximal transport (K0.5Na) was 36.1 mM. Na+-dependent 5-ASA uptake was competitively inhibited by nicotinate with an inhibitory constant (Ki) of 2.1 mM was comparable to the Km value of Na+-dependent nicotinate uptake (0.99 mM). Furthermore, ibuprofen, a selective SMCT1 inhibitor, was found to have a significantly inhibitory effect on the Na+-dependent 5-ASA uptake in mouse colon (IC50 = 0.19 mM). Taken collectively, these results indicated that SMCT1 in the mouse colonic mucosa is responsible for Na+-dependent 5-ASA uptake.