The Role of Interleukin-23 in the Early Development of Emphysema in HIV1+ Smokers [RNA-seq]

Matrix metalloproteinase-9 (MMP-9) expression is up-regulated in alveolar macrophages (AM) of HIV1+ smokers who develop emphysema. Based on the knowledge that lung epithelial lining fluid (ELF) of HIV1+ smokers has increased levels of inflammatory cytokines compared to HIV1- smokers, we hypothesized up-regulation of lung cytokines in HIV1+ smokers may be functionally related to increased MMP-9 expression. Cytokine arrays evaluated cytokine protein levels in ELF obtained from 5 groups of individuals: HIV1‾ healthy nonsmokers, HIV1‾ healthy smokers, HIV1‾ smokers with low diffusing capacity (DLCO) , HIV1 + nonsmokers, and HIV1 + smokers with low DLCO. Among several pro-inflammatory cytokines elevated in ELF associated with smoking and HIV1+, increased levels of the Th17-related cytokine IL-23 were found in HIV1- smokers with low DLCO and HIV1+ smokers and nonsmokers. Relative IL-23 gene expression was significantly increased in AM of HIV1+ individuals, with greater expression in AM of HIV1+ smokers with low DLCO. Infection with HIV1 in vitro induced IL-23 expression in normal AM. Since AM purified by adherence contain a small number of lymphocytes, we hy-pothesized that in an AM/lymphocyte co-culture system, IL-23 would up-regulate MMP-9. IL-23 stimulation of AM/lymphocyte co-cultures in vitro induced increased MMP-9 mRNA levels and protein. AM of healthy individuals did not express IL-23 receptors (IL-23R), lung T lymphocytes express IL-23R and interact with AM in order to up-regulate MMP-9. This mechanism may contribute to the increased tissue destruction in the lungs of HIV1+ smokers and suggests that Th-17 related inflammation may play a role. IL-23 upregulates MMP-9 expression in human alveolar macrophages via a T lymphocyte/alveolar macrophage interaction, suggesting a possible role for Th-17 related inflammation in accelerated emphysema in HIV1+ smokers.