Renin-Angiotensin System in Central Nervous System Diseases and its Interaction with COVID-19

Background: The Renin-Angiotensin System (RAS) comprises a complex molecular cascade with two counter-regulatory axes, the classical and the alternative. Angiotensin II and Angiotensin-(1-7), the main peptides of the RAS, exert opposite effects in multiple organs and systems, including the cardiovascular, renal, pulmonary, and immune systems. Strong evidence supports the hypothesis of a local RAS in the Central Nervous System (CNS) and its modulatory roles in neuroendocrinology and neurotransmission. Objective: In this narrative review, we provide a comprehensive approach to experimental and clinical data regarding RAS molecule expression and their possible roles in the physiology and physiopathology of CNS diseases. Methods: This non-systematic review summarizes evidence on RAS implications in CNS diseases and their possible relationships with COVID-19. Results: We divided the possible RAS mechanisms in distinct conditions during the lifespan, approaching from congenital infections to neurodegenerative alterations, passing through mood disorders and cerebrovascular diseases. We also gathered current evidence about the possible effects of RAS in Covid-19, particularly in cases with neurological manifestations. Conclusion: Although there are limitations and controversies, the analysis of RAS mechanisms in the CNS certainly represents an interesting field of research. However, further investigation is necessary to support the noteworthy interactions and provide a better comprehension of the cross-talk between RAS and the CNS. Investigations in this research field may shed light on the novel therapeutic targets.