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Most patients with COVID-19 in the intensive care unit develop an acute respiratory distress syndrome characterized by severe hypoxemia, decreased lung compliance, and high vascular permeability. Activation of the complement system is a hallmark of moderate and severe COVID-19, with abundant deposition of complement proteins in inflamed tissue and on the endothelium during COVID-19. Using a transgenic mouse model of SARS-CoV-2 infection, we assessed the therapeutic utility of an inhibitory antibody (HG4) targeting MASP-2, a key enzyme in the lectin pathway. Treatment of infected mice with HG4 reduced the disease severity score and improved survival vs mice that received an isotype control antibody. Administration of HG4 significantly reduced the lung injury score, including alveolar inflammatory cell infiltration, alveolar edema, and alveolar hemorrhage. The ameliorating effect of MASP-2 inhibition on the severity of COVID-19 pathology is reflected by a significant reduction in the proinflammatory activation of brain microglia in HG4-treated mice. [ABSTRACT FROM AUTHOR]

Objective: Reduced folate carrier 1 (RFC1) is highly expressed in central nervous system microvessels and have a role in folate transport. Recently, we found RFC1 increase in mice retina by ischemia. Here, we assessed whether RFC1 also changes in human brain microvascular endothelial cell cultures (hBMECs) by ischemia. We also investigated if RFC1 is expressed in brain tissue macrophages derived from induced pluripotent stem cells (IPSC), hence could be used in further studies. Methods: We subjected hBMECs to 16 hours of hypoxia (0.5% O2) and 4 hours of re-oxygenation in the presence of human serum. From human episomal IPSC, embryoid bodies were formed and cultured. Then, non-adherent cells were collected and preserved for 10 days in the media to obtain mature tissue macrophages (TM). hBMECs (n=4), embryoid bodies (n=7), and mature TMs (n=8) were harvested, homogenized and total RNA were extracted. RFC1 gene expression was assessed by qRT-PCR. Statistical analyses were performed with PRISM v.9. Results: In hBMECs, RFC1 mRNA increased via hypoxia and re-oxygenation by 35-fold when compared to controls (t-test, p<0.01). Secondly, RFC1 mRNA was expressed in cells derived from IPSCs, and was higher in the immature embryoid body stage compared to mature TM (33%, t-test, p<0.01). Conclusion: The increase of RFC1 expression in hBMECs by ischemia supports our previous results in mouse model of retinal ischemia. As such, RFC1 is accountable as a pathological mechanism activated in ischemic microvessels and could be a promising new target. Moreover, in terms of IPSC derived macrophages, the high RFC1 expression in their immature states is concordant with the embyonic development in human, and strenghtens the reliability of usage of these cells to study RFC1 in brain microvessels. [ABSTRACT FROM AUTHOR]