Prolonged exposure to lung-derived cytokines is associated with inflammatory activation of microglia in patients with COVID-19

Neurological impairment is the most common finding in patients with post-acute sequelae of COVID-19. Furthermore, survivors of pneumonia from any cause have an elevated risk of dementia(1–4). Dysfunction in microglia, the primary immune cell in the brain, has been linked to cognitive impairment in murine models of dementia and in humans(5). Here, we report a transcriptional response in human microglia collected from patients who died following COVID-19 suggestive of their activation by TNF-α and other circulating pro-inflammatory cytokines. Consistent with these findings, the levels of 55 alveolar and plasma cytokines were elevated in a cohort of 341 patients with respiratory failure, including 93 unvaccinated patients with COVID-19 and 203 patients with other causes of pneumonia. While peak levels of pro-inflammatory cytokines were similar in patients with pneumonia irrespective of etiology, cumulative cytokine exposure was higher in patients with COVID-19. Corticosteroid treatment, which has been shown to be beneficial in patients with COVID-19(6), was associated with lower levels of CXCL10, CCL8, and CCL2—molecules that sustain inflammatory circuits between alveolar macrophages harboring SARS-CoV-2 and activated T cells(7). These findings suggest that corticosteroids may break this cycle and decrease systemic exposure to lung-derived cytokines and inflammatory activation of microglia in patients with COVID-19.