Mycoplasma ovipneumoniae induces caspase-8-dependent extrinsic apoptosis and p53- and ROS-dependent intrinsic apoptosis in murine alveolar macrophages

Mycoplasma ovipneumoniae (MO) is a principle causative agent of chronic respiratory disease in ruminants, including sheep, goats, and deer, posing a great threat to the ruminant industry worldwide. However, the pathogenesis of MO infection still remains not well understood and needs further clarification. Here we report a time-dependent apoptosis in cultured murine alveolar macrophage (MH-S) cell lines in response to MO infection in vitro. Mechanistically, MO infection activated apoptosis in MH-S cells through caspase-8-dependent extrinsic pathway and through tumor protein 53 (p53)- and reactive oxygen species (ROS)-dependent intrinsic mitochondrial pathways. Moreover, MO infection promoted both transcription and translation of proinflammatory cytokine genes including interleukin-1β (IL-1β), IL-18, and tumor necrosis factor-α (TNF-α), in a caspase-8-, p53-, and ROS-dependent manner, implying a potential link between MO-induced inflammation and apoptotic cell death. Collectively, our results suggest that MO infection induces the activation of extrinsic and intrinsic apoptotic pathways in cultured MH-S cells, which is related to upregulated expression of proinflammatory cytokines. Our findings will contribute to the elucidation of pathogenesis in MO infection and provide valuable reference for the development of new strategies for controlling MO infection.