Inflammation and Coagulation in Neurologic and Psychiatric Disorders

Coagulation factors are intrinsically expressed in various brain cells, including astrocytes and microglia. Their interaction with the inflammatory system is important for the well-being of the brain, but they are also crucial in the development of many diseases in the brain such as stroke and traumatic brain injury. The cellular effects of coagulation are mediated mainly by protease-activated receptors. In this review, we sum up the role of the coagulation cascade in the development of different diseases including psychiatric disorders. In inflammatory diseases such as multiple sclerosis, fibrinogen activates microglia and suppresses the differentiation of oligodendrocytes, leading to axonal damage and suppression of remyelination. In ischemic stroke, thrombin activity is associated with the size of infarction, and the inhibition of either thrombin- or protease-activated receptor 1 promotes neuronal survival and reduces the size of infarction. Patients suffering from Alzheimer's disease express higher levels of thrombin, which in turn damages the endothelium, increases blood-brain barrier permeability, and induces cell apoptosis. In major depressive disorder, a positive correlation is present between prothrombotic states and suicidality. Moreover, both protein S deficiency and antiphospholipid antibodies are associated with schizophrenia and there is an effect of warfarin on psychosis-free intervals. Studying the coagulation in the brain could open a new door in understanding and treating neurological and psychiatric disorders, and extensive research should be conducted in this field.