Neospora Caninum Infection Induced Mitochondrial Dysfunction in Caprine Endometrial Epithelial Cells Via Downregulating SIRT1

Background: Infection of Neospora caninum, an important obligate intracellular protozoan parasite, causes reproductive dysfunctions (e.g. abortions) in ruminants (e.g. cattle, sheep and goats), leading to serious economic losses of livestock worldwide, but the pathogenic mechanisms of N. caninum are poorly understood. Mitochondrial dysfunction has been reported to be closely associated with pathogenesis of many infectious diseases. However, the effect of N. caninum infection on the mitochondrial function of hosts remains unclear.

Methods: The effects of N. caninum infection on mitochondrial dysfunction in caprine endometrial epithelial cells (EECs), including intracellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) contents, mitochondrial DNA (mtDNA) copy numbers and ultrastructure of mitochondria, were studied by using JC-1, DCFH-DA, ATP assay kits, quantitative real-time polymerase chain reaction (RT-qPCR) and transmission electron microscopy, respectively, and the regulatory roles of sirtuin 1 (SIRT1) on mitochondrial dysfunction, autophagy and N. caninum propagation in caprine EECs were investigated by using two drugs, namely resveratrol (an activator of SIRT1) and Ex 527 (an inhibitor of SIRT1).

Results: The current study found that N. caninum infection induced mitochondrial dysfunction of caprine EECs, including accumulation of intracellular ROS, significant reductions of MMP, ATP contents, mtDNA copy numbers and damaged ultrastructure of mitochondria. Downregulated expression of SIRT1 was also detected in caprine EECs infected with N. caninum. Treatments using resveratrol and Ex 527 to caprine EECs showed that dysregulation of SIRT1 significantly reversed mitochondrial dysfunction of cells caused by N. caninum infection. Furthermore, using resveratrol and Ex 527, SIRT1 expression was found to be negatively associated with autophagy induced by N. caninum infection in caprine EECs, and the intracellular propagation of N. caninum tachyzoites in caprine EECs was negatively affected by SIRT1 expression.

Conclusions: These results indicated that N. caninum infection induced mitochondrial dysfunction by downregulating SIRT1, and downregulation of SIRT1 promoted cell autophagy and intracellular proliferation of N. caninum tachyzoites in caprine EECs. The findings suggested a potential role of SIRT1 as a target to develop control strategies against N. caninum infection.