C57-01 The Effect of PM2.5 and SARS-CoV-2 on ACE2 and TMPSS2 Expression and Anti-Viral Response in Calu-3 Airway Epithelial Cells

Abstract Rationale Although studies have shown that air pollutants affect SARS-CoV-2 infection severity, the underlying mechanisms remain unclear. Our aim was to investigate the impacts of particulate matter less than 2.5 um (PM2.5) and SARS-CoV-2 on inflammatory changes and inflammasomal responses of Calu-3 cells. Methods Calu-3 airway epithelial cells were exposed to PM2.5 at concentrations of 10, 50, and 100 ug/mL, and to SARS-CoV-2 at an MOI of 0.01 for 24 hours. Cell viability was evaluated by the MTT assay, and epithelial barrier integrity was assessed through immunofluorescence staining of Zonula Occludens-1. The mRNA expression of viral entry genes—angiotensin-converting enzyme (ACE)2 and transmembrane protease serine (TMPRSS)2—as well as inflammatory and inflammasome-related genes including interleukin (IL)-8, IL-6, nuclear factor (NF)-kB p65 (RELA), JNK, c-JUN, Caspase-1 (CASP1), IL-1B, NLRP3, and interferon gamma (IFNg) was analyzed using qRT-PCR. Intracellular viral spike protein levels and RNA-dependent RNA polymerase (RdRP) expression were examined by immunofluorescence staining and qRT-PCR, respectively, while the release inflammatory cytokines were analyzed by ELISA. Results Higher concentrations of 100ug/mL PM2.5 reduced Calu-3 cell viability (p = 0.02) and damaged epithelial barrier integrity. PM2.5 (50ug/ml) increased mRNA expression for ACE2 and TMPRSS2 (p 0.01). While PM2.5 alone decreased c-JUN expression, it did not change mRNA levels of JNK and RELA. In contrast, a co-incubation of SARS-CoV-2 and PM2.5 significantly increased mRNA levels for JNK and RELA (p 0.05 and p 0.01, respectively) and decreased c-JUN expression (p 0.01). Additionally, exposure to PM2.5 and lower concentrations of PM2.5 + SARS-CoV-2 led to increased expression of IL-1B, IL-6, and GM-CSF, whereas IL-8 was induced only by SARS-CoV-2. Co-incubation with higher concentrations of PM2.5 (50 and 100 ug/mL) and SARS-CoV-2 decreased the expression of IL-8, IL-1B, CASP-1, and IFNg compared to their respective control groups. Lastly, both 50 ug/mL PM2.5 and SARS-CoV-2 led to an increase in the viral load (RdRP) (p 0.05). Conclusions Our results show that PM2.5 impair epithelial integrity and cell viability, raises mRNA levels of ACE2 and TMPRSS2, and causes inflammation in Calu-3 cells exposed to SARS-CoV-2. These results suggest that PM2.5 may facilitate SARS-CoV-2 entry into airway epithelial cells, and that both PM2.5 and SARS-CoV-2 can deteriorate the host cell’s inflammatory and antiviral defenses. This abstract is funded by: Turkish Thoracic Society