Clozapine Induces Myocardial Inflammation Response Through Lactation Modification---Based on Novel Tree Shrew Models of Schizophrenia

Abstract

Background

Schizophrenia is a mental disorder with a high disability rate, and patients almost lose their social functions. Clozapine is an effective drug for the treatment of refractory schizophrenia. However, recent studies have found that schizophrenic patients treated with clozapine have progressive cardiac dysfunction related to lactate accumulation. Tree shrews belong to primates, which are genetically closer to humans. Using a tree shrew to establish a schizophrenic model is helpful for the study of the pathogenesis of schizophrenia and related accompanying diseases. It is significant to reveal the mechanism of clozapine-induced cardiac damage by different models of schizophrenia.

Methods:The tree shrew schizophrenic models were established by using MK801 and virus-induced, respectively. The tree shrew-specific maze (homing maze) independently developed by the research team was used to determine the model establishment and evaluate the tree shrew's cognitive impairment. The MK801 group was treated with clozapine (gavage) for 4 weeks, and the virus-induced group was treated with clozapine (gavage) for 5 weeks. The myocardial enzymes, electrocardiogram and left ventricular ejection fraction of tree shrew model were measured, the changes of lactate level were analyzed by biochemical method, the myocardial inflammatory was analyzed by immunohistochemistry, and pan-lactated protein was detected by western-blot. The effects of clozapine and lactic acid on TNF-α, IL-1β and IL-10 were determined in vitro using cultured human cardiomyocytes.

Results:Compared with the standard control group, the two groups of schizophrenic tree shrews had apparent cognitive impairment, and the maze time (homing time) was significantly prolonged, confirming that the model was successfully established. Compared with the model group, clozapine treatment shortened the homing time, and the difference was statistically significant (P<0.01). The electrocardiogram examination showed that compared with the model group, the tree shrews in the clozapine treatment group had a slower heart rate, longer Q-T interval, and significantly lower ST segment (P<0.01). In the clozapine groups, the Myocardial enzymes were higher than those in the model groups (CK-MB (P<0.05), LDH (P<0.05) and cTnI (P<0.01)). Echocardiography showed that the left ventricular ejection fraction of tree shrew in the clozapine groups was lower than that in the model group (P<0.05). The serum lactate in the clozapine treatment groups was significantly increased, accompanied by the accumulation of a large number of monocytes and multinucleated giant cells in myocardial tissue. After MK-8012 was discontinued for 2 weeks, the serum lactate decreased, and the accumulation of monocytes and multinucleated giant cells in myocardial tissue decreased. Western blot showed that clozapine increased the expression of the pan-lactated protein in the myocardium of tree shrews. In vitro studies showed that clozapine increased the expression of TNF-α and IL-1β in the supernatant of cultured human cardiomyocytes (P<0.01) and decreased the expression of anti-inflammatory factor IL-10 (P<0.05). Sodium lactate further exacerbates the inflammatory response caused by clozapine.

Conclusion: Both MK801 and virus can effectively establish a tree shrew schizophrenic model. Clozapine-treated tree shrew models of schizophrenia showed it decreased cardiac function, which might be related to cardiac inflammatory response due to lactic acid accumulation.