Solar simulated ultraviolet radiation inactivates HCoV-NL63 and SARS-CoV-2 coronaviruses at environmentally relevant doses

The germicidal properties of short wavelength ultraviolet C (UVC) light are well established and used to inactivate many viruses and other microbes. However, much less is known about germicidal effects of terrestrial solar UV light, confined exclusively to wavelengths in the UVA and UVB regions. Here, we have explored the sensitivity of the human coronaviruses HCoV-NL63 and SARS-CoV-2 to solar-simulated full spectrum ultraviolet light (sUV) delivered at environmentally relevant doses. First, HCoV-NL63 coronavirus inactivation by sUV-exposure was confirmed employing (i) viral plaque assays, (ii) RT-qPCR detection of viral genome replication, and (iii) infection-induced stress response gene expression array analysis. Next, a detailed dose-response relationship of SARS-CoV-2 coronavirus inactivation by sUV was elucidated, suggesting a half maximal suppression of viral infectivity at low sUV doses. Likewise, extended sUV exposure of SARS-CoV-2 blocked cellular infection as revealed by plaque assay and stress response gene expression array analysis. Moreover, comparative (HCoV-NL63 versus SARS-CoV-2) single gene expression analysis by RT-qPCR confirmed that sUV exposure blocks coronavirus-induced redox, inflammatory, and proteotoxic stress responses. Based on our findings, we estimate that solar ground level full spectrum UV light impairs coronavirus infectivity at environmentally relevant doses. Given the urgency and global scale of the unfolding SARS-CoV-2 pandemic, these prototype data suggest feasibility of solar UV-induced viral inactivation, an observation deserving further molecular exploration in more relevant exposure models.

Induction of Pluripotent Stem Cell-Derived Cardiomyocyte Toxicity by Supernatant of Long Term-Stored Red Blood Cells in Vitro

Background/Aims: Preserved red blood cells (RBCs) in vitro undergo a series of morphological, functional and metabolic changes during storage. RBC metabolites accumulate over time during storage, the toxicity of the supernatants of RBCs (SSRBCs) on tissue cells is largely unknown. Here, we aimed to study cardiomyocyte toxicity by supernatant of long term-stored RBCs in vitro and to discover elements involved in the mechanism. Methods: Using human-induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) and real-time cell analyzing (RTCA), we analyzed the cardiotoxicity of d0, d14 and d35 SSRBCs. To analyze the cardiotoxicity of potassium (K) and lactic acid (LA) in SSRBCs, solutions containing the same concentrations of K and LA were respectively prepared and co-cultured with hiPS-CMs. Immunofluorescence and Gene Expression Array of hiPS-CMs were performed to evaluate the effects of d35 K and d35 SSRBCs. Results: The beating of hiPS-CM was stopped by d14, d35 SSRBCs, or d35 K solution. Beating resumed within 48 hours in the presence of d14 SSRBC or d35 K but not d35 SSRBC; d0, d14 and d35 LA solution had no effect on beating patterns. At 48h after treatment, the immunofluorescence results showed that the integrity of the filament and sarcomere were intact. Gene Expression Array results found 14 differentially expressed genes which were likely to play an important role in the cytotoxic effect. Conclusion: Our results demonstrated cardiomyocyte toxicity by long term-stored SSRBCs in vitro. Besides high K-induced cardiotoxicity, there must be other unknown components in long term-stored SSRBCs that are cytotoxic to hiPS-CMs.