Prominent Anti-UVC Activity of Lignin Degradation Products.

BACKGROUND/AIM: The rapid spread of COVID-19 resulted in the revision of the value of ultraviolet C (UVC) sterilization in working spaces. This study aimed at re-evaluating the anti-UVC activity of four groups of natural products against human melanoma COLO679 and human normal dermal fibroblast (HDFa) cells, based on chemotherapeutic index. MATERIALS AND METHODS: Various cell lines were exposed to UVC for 3 min in the presence of increasing concentrations of test compounds and viable cell numbers were determined with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The anti-UVC activity was quantified by the ratio of the 50% cytotoxic concentration (determined without irradiation) to the 50% effective concentration (which abolished by 50% the UVC-induced loss of viability). Apoptosis was quantified as the subG1 population proportion following cell-cycle analysis. RESULTS: Among four groups of major natural products, six phenylpropanoids showed the highest anti-UVC activity, followed by the lignified products and alkaline products that contain lignin and its degradation products. On the other hand, tannins and flavonoids showed lower activity due to their higher cytotoxicity. UVC-sensitive COLO679 cells lack dectin-1 protein expression. CONCLUSION: These data suggest the prominent anti-UVC activity of lignin degradation products, and the possible involvement of dectin-1 expression in UVC-sensitivity.

Comparison of UVC Sensitivity and Dectin-2 Expression Between Malignant and Non-malignant Cells.

BACKGROUND/AIM: Rapid spread of COVID-19 resulted in the revision of the value of ultraviolet C (UVC) sterilization in working spaces. This study aimed at investigating the UVC sensitivity of eighteen malignant and nonmalignant cell lines, the protective activity of sodium ascorbate against UVC, and whether Dectin-2 is involved in UVC sensitivity. MATERIALS AND METHODS: Various cell lines were exposed to UVC for 3 min, and cell viability was determined using the MTT assay. Anti-UV activity was determined as the ratio of 50% cytotoxic concentration (determined with unirradiated cells) to 50% effective concentration (that restored half of the UV-induced loss of viability). Dectin-2 expression was quantified using flow cytometry. RESULTS: The use of culture medium rather than phosphate-buffered saline is recommended as irradiation solution, since several cells are easily detached during irradiation in phosphate-buffered saline. Oral squamous cell carcinoma cell lines showed the highest UV sensitivity, followed by neuroblastoma, glioblastoma, leukemia, melanoma, lung carcinoma cells, and normal oral and dermal fibroblasts. Human dermal fibroblasts were more resistant than melanoma cell lines; however, both expressed Dectin-2. Sodium ascorbate at micromolar concentrations eliminated the cytotoxicity of UVC in these cell lines. CONCLUSION: Normal cells are generally UVC-resistant compared to corresponding malignant cells, which have higher growth potential. Dectin-2 protein expression itself may not be determinant of UVC sensitivity.

A New Method for Testing Filtration Efficiency of Mask Materials Under Sneeze-like Pressure.

BACKGROUND: Sneezes produce many pathogen-containing micro-droplets with high velocities of 4.5-50.0 m/s. Face masks are believed to protect people from infection by blocking those droplets. However, current filtration efficiency tests can't evaluate masks under sneeze-like pressure. The goal of this study was to establish a method to evaluate the filtration efficiency of mask materials under extreme conditions. MATERIALS AND METHODS: Efficiency of surgical masks, gauze masks, gauze, cotton, silk, linen and tissue paper on blocking micro-droplet sized starch particles (average 8.2 µm) and latex microspheres (0.75 µm) with a velocity of 44.4 m/s created by centrifugation was qualitatively analyzed by using imaging-based analysis. RESULTS: The 4 layers of silk could block 93.8% of microspheres and 88.9% of starch particles, followed by the gauze mask (78.5% of microspheres and 90.4% of starch particles) and the 2 layers of cotton (74.6% of microspheres and 87.5-89.0% of particles). Other materials also blocked 53.2-66.5% of microspheres and 76.4%-87.9% of particles except the 8 layers of gauze which only blocked 36.7% of particles. The filtration efficiency was improved by the increased layers of materials. CONCLUSION: Centrifugation-based filtration efficiency test not only compensates shortcomings of current tests for masks, but also offers a simple way to explore new mask materials during pandemics. Common mask materials can potentially provide protection against respiratory droplet transmission.

ACE2: The key Molecule for Understanding the Pathophysiology of Severe and Critical Conditions of COVID-19: Demon or Angel?

Recently, the SARS-CoV-2 induced disease COVID-19 has spread all over the world. Nearly 20% of the patients have severe or critical conditions. SARS-CoV-2 exploits ACE2 for host cell entry. ACE2 plays an essential role in the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure and fluid balance. ACE2 also protects organs from inflammatory injuries and regulates intestinal functions. ACE2 can be shed by two proteases, ADAM17 and TMPRSS2. TMPRSS2-cleaved ACE2 allows SARS-CoV-2 cell entry, whereas ADAM17-cleaved ACE2 offers protection to organs. SARS-CoV-2 infection-caused ACE2 dysfunction worsens COVID-19 and could initiate multi-organ failure. Here, we will explain the role of ACE2 in the pathogenesis of severe and critical conditions of COVID-19 and discuss auspicious strategies for controlling the disease.