Regulation of versican expression by bacterial infection is TLR4‐dependent but MyD88‐independent (1046.3)

Abstract

In the acute response to bacterial lung infection, gram‐negative bacteria activation of toll‐like receptors (TLRs) stimulates macrophages to secrete a variety of molecules that lead initially to pulmonary inflammation and, ultimately, to resolution of inflammation. Using immunohistochemistry and qPCR we have shown that versican, a chondroitin sulfate proteoglycan, co‐localizes with macrophages in the lungs of mice with gram‐negative pneumonia, and is produced by alveolar and bone marrow‐derived macrophages (BMDM) exposed to live E. coli or lipopolysaccharide (LPS) in vitro. The goal of the current study is to define the TLR signaling pathway responsible for versican production by macrophages. BMDM were isolated from wild‐type mice (WT) and mice lacking TLR2 (TLR2 KO), TLR4 (TLR4 KO), or MyD88 (MyD88 KO). Versican mRNA was detected at low levels in untreated BMDM from all mice. In WT BMDM, versican mRNA was significantly increased by 4 h after treatment with 10 ng/ml LPS (50.5 ± 10.8‐fold vs PBS control; n = 3, p < 0.0001), and returned to basal levels by 24 h. The versican response to LPS was similarly elevated in TLR2 KO BMDM but was completely abrogated in TLR4 KO BMDM, indicating that LPS induction of versican is mediated by TLR4. Further, the response in MyD88 KO BMDM (48.3 ± 5.0‐fold vs PBS control; n = 3, p < 0.0001) was similar to that in WT BMDM, indicating that LPS induction of versican is MyD88‐independent. Further studies to define downstream signaling components in more detail are in process and will contribute to our understanding of the pro‐ vs anti‐inflammatory role of versican in the acute response to bacterial infection.Grant Funding Source: Supported by HL098067 & RR030249