Vimentin affects inflammation and neutrophil recruitment in airway epithelium during Streptococcus suis serotype 2...

Streptococcus suis serotype 2 (SS2) frequently colonizes the swine upper respiratory tract and can cause Streptococcal disease in swine with clinical manifestations of pneumonia, meningitis, and septicemia. Previously, we have shown that vimentin, a kind of intermediate filament protein, is involved in the penetration of SS2 through the tracheal epithelial barrier. The initiation of invasive disease is closely related to SS2-induced excessive local inflammation; however, the role of vimentin in airway epithelial inflammation remains unclear. Here, we show that vimentin deficient mice exhibit attenuated lung injury, diminished production of proinflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and the IL-8 homolog, keratinocyte-derived chemokine (KC), and substantially reduced neutrophils in the lungs following intranasal infection with SS2. We also found that swine tracheal epithelial cells (STEC) without vimentin show decreased transcription of IL-6, TNF-α, and IL-8. SS2 infection caused reassembly of vimentin in STEC, and pharmacological disruption of vimentin filaments prevented the transcription of those proinflammatory cytokines. Furthermore, deficiency of vimentin failed to increase the transcription of nucleotide oligomerization domain protein 2 (NOD2), which is known to interact with vimentin, and the phosphorylation of NF-κB protein p65. This study provides insights into how vimentin promotes excessive airway inflammation, thereby exacerbating airway injury and SS2-induced systemic infection.