[Staphylococcus aureus promotes NOD2 expression in bovine mammary epithelial cells]

Objective To investigate the role of nucleotide-binding oligomerization domain-containing protein 2 (NOD2) in the mediate recognition of Staphylococcus aureus (S. aureus) in bovine mammary epithelial cells (BMECs). Methods We infected BMECs with living S. aureus and heat-inactivated S. aureus, respectively. When the multiplicity of infection (MOI) of living S. aureus was set for 100:1, the infection time were 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4 hours; when the MOI of living S. aureus was set for 10:1, 20:1, 40:1, 100:1, the infection time was 2 hours; on the other hand, 0, 10⁴, 10⁵, 10⁶, 10⁷, 10⁸ colony-forming units (CFU)/mL of heat-inactivated S. aureus were used to infect the cells for 2 hours separately. The expression of NOD2 was detected using real-time PCR and Western blotting. Results Levels of NOD2 mRNA and protein expression significantly increased after 0.5-4 hours of infection with living S. aureus. When the cells were infected with S. aureus at different MOI, dose-dependent accumulation of NOD2 mRNA and protein could be detected in BMECs. Levels of NOD2 mRNA and protein expression were not significantly upregulated by the stimulation with heat-inactivated S. aureus. Conclusion S. aureus infection could induce the up-regulation of NOD2 expression in BMECs.