Therapeutic Potential of the Purinergic System in Major Depressive Disorder Associated with COVID-19.

Neuroinflammation is closely related to the development of depression, since the latter is caused, among other factors, by inflammatory processes, mainly related to the activation of microglia and expression of specific genes, which occurs during the neuroinflammatory process. Thus, COVID-19 is an important risk factor for the development of depression, since in addition to generating the feeling of stress, which also increases the activity of the immune system, it is also the cause of pathological processes and physiological ones that lead to the development of neuroinflammation, microglial activation, gene expression dysfunction and decreased concentration of available serotonin. That said, drugs are being used to combat COVID-19 to reduce the oxidative stress presented in the disease. Thus, tramadol and fluoxetine are highlighted as drugs used, however, although they present some positive results, such as the reduction of pro-inflammatory cytokines, they are also associated with negative effects such as dependence, pulmonary, cardiac and brain impairment. From this, the purinergic system is highlighted in the literature as a possible therapeutic target. This is because its mechanisms are related to the regulation of microglia, astrocytes and the physiology of important neurotransmitters and hormones. Added to this, there is a modulation of inflammatory activity, especially with regard to the P2X7 receptors of this system. The latter is an important target for the treatment of depression and COVID-19, since positive results were obtained through the genetic exclusion of this receptor and the use of selective antagonists.