Wong AC, Devason AS, Umana IC, Cox TO, Dohnalová L, Litichevskiy L, Perla J, Lundgren P, Etwebi Z, Izzo LT, Kim J, Tetlak M, Descamps HC, Park SL, Wisser S, McKnight AD, Pardy RD, Kim J, Blank N, Patel S, Thum K, Mason S, Beltra JC, Michieletto MF, Ngiow SF, Miller BM, Liou MJ, Madhu B, Dmitrieva-Posocco O, Huber AS, Hewins P, Petucci C, Chu CP, Baraniecki-Zwil G, Giron LB, Baxter AE, Greenplate AR, Kearns C, Montone K, Litzky LA, Feldman M, Henao-Mejia J, Striepen B, Ramage H, Jurado KA, Wellen KE, O’Doherty U, Abdel-Mohsen M, Landay AL, Keshavarzian A, Henrich TJ, Deeks SG, Peluso MJ, Meyer NJ, Wherry EJ, Abramoff BA, Cherry S, Thaiss CA, Levy M. Serotonin reduction in post-acute sequelae of viral infection. Cell. 2023 Oct 26;186(22):4851-4867.e20. doi: 10.1016/j.cell.2023.09.013. Epub 2023 Oct 16. PMID: 37848036.
Abstract
Post-acute sequelae of COVID-19 (PASC, “Long COVID”) pose a significant global health challenge. The pathophysiology is unknown, and no effective treatments have been found to date. Several hypotheses have been formulated to explain the etiology of PASC, including viral persistence, chronic inflammation, hypercoagulability, and autonomic dysfunction. Here, we propose a mechanism that links all four hypotheses in a single pathway and provides actionable insights for therapeutic interventions. We find that PASC are associated with serotonin reduction. Viral infection and type I interferon-driven inflammation reduce serotonin through three mechanisms: diminished intestinal absorption of the serotonin precursor tryptophan; platelet hyperactivation and thrombocytopenia, which impacts serotonin storage; and enhanced MAO-mediated serotonin turnover. Peripheral serotonin reduction, in turn, impedes the activity of the vagus nerve and thereby impairs hippocampal responses and memory. These findings provide a possible explanation for neurocognitive symptoms associated with viral persistence in Long COVID, which may extend to other post-viral syndromes.