Interleukin-32β Propagates Vascular Inflammation and Exacerbates Sepsis in a Mouse Model

BACKGROUND: Inflammation is associated with most diseases, which makes understanding the mechanisms of inflammation vitally important. METHODOLOGY/PRINCIPAL FINDINGS: Here, we demonstrate a critical function of interleukin-32β (IL-32β) in vascular inflammation. IL-32β is present in tissues from humans, but is absent in rodents. We found that the gene is highly expressed in endothelial cells. Three isoforms of IL-32, named IL-32α, β, and ε, were cloned from human endothelial cells, with IL-32β being the major isoform. Pro-inflammatory cytokines (TNFα and IL-1β) induced IL-32β expression through NF-κB. Conversely, IL-32β propagated vascular inflammation via induction of vascular cell adhesion molecules and inflammatory cytokines. Accordingly, IL-32β increased adhesion of inflammatory cells to activated endothelial cells, a paramount process in inflammation. These results illustrate a positive feedback regulation that intensifies and prolongs inflammation. Importantly, endothelial/hematopoietic expression of IL-32β in transgenic mice elevated inflammation and worsened sepsis. This was demonstrated by significant elevation of leukocyte infiltration and serum levels of TNFα and IL-1β, increased vascular permeability and lung damage, and accelerated animal death. Together, our results reveal an important function of IL-32 in vascular inflammation and sepsis development. CONCLUSIONS/SIGNIFICANCE: Our results reveal an important function of IL-32 in vascular inflammation and sepsis development.