Follow-up of patients affected by COVID-19 has unveiled remarkable findings. Among the several sequelae caused by SARS-CoV-2 viral infection, it is particularly noteworthy that patients are prone to developing depression, anxiety, cognitive disorders, and dementia as part of the post-COVID-19 syndrome. The multisystem aspects of this disease suggest that multiple mechanisms may converge towards post-infection clinical manifestations. The literature provides mechanistic hypotheses related to changes in classical neurotransmission evoked by SARS-CoV-2 infection; nonetheless, the interaction of peripherally originated classical and non-canonic peptidergic systems may play a putative role in this neuropathology. A wealth of robust findings shows that hemoglobin-derived peptides are able to control cognition, memory, anxiety, and depression through different mechanisms. Early erythrocytic death is found during COVID-19, which would cause excess production of hemoglobin-derived peptides. Following from this premise, the present review sheds light on a possible involvement of hemoglobin-derived molecules in the COVID-19 pathophysiology by fostering neuroscientific evidence that supports the contribution of this non-canonic peptidergic pathway. This rationale may broaden knowledge beyond the currently available data, motivating further studies in the field and paving ways for novel laboratory tests and clinical approaches.
Keywords: COVID-19; SARS-CoV-2; hemoglobin; hemopressins; hemorphins; neurology; neurotransmitters; psychiatry.