The Role of Chloroquine and Hydroxychloroquine in Immune Regulation and Diseases

Chloroquine (CQ) and hydroxychloroquine (HCQ) are derivatives of the heterocyclic aromatic compound quinoline. These economical compounds have been used as antimalarial agents for many years. Currently, they are used as monotherapy or in conjunction with other therapies for the treatment of autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjögren's syndrome (SS) and antiphospholipid antibody syndrome (APS). Based on its effects on the modulation of the autophagy process, various clinical studies suggest that CQ and HCQ could be used in combination with other chemotherapeutics for the treatment of various types of cancer. Furthermore, the antiviral effects showed against Zika, Chikungunya, and HIV are due to the annulation of endosomal/lysosomal acidification. Recently, CQ and HCQ were approved for the U.S. Food and Drug Administration (FDA) for the treatment of infected patients with the coronavirus SARSCoV- 2, causing the disease originated in December 2019, namely COVID-2019. Several mechanisms have been proposed to explain the pharmacological effects of these drugs: 1) disruption of lysosomal and endosomal pH, 2) inhibition of protein secretion/expression, 3) inhibition of antigen presentation, 4) decrease of proinflammatory cytokines, 5) inhibition of autophagy, 6) induction of apoptosis and 7) inhibition of ion channels activation. Thus, evidence has shown that these structures are leading molecules that can be modified or combined with other therapeutic agents. In this review, we will discuss the most recent findings in the mechanisms of action of CQ and HCQ in the immune system, and the use of these antimalarial drugs on diseases.