Abstract 5546: Krüppel-like Factor 2 (KLF)2 Inhibits Macrophage Pro-inflammatory Activation
Background: Inflammation contributes to a broad spectrum of human disease states including cardiovascular disease. Macrophages are critical regulators of the innate inflammatory response. KLF2 is a member of the Krüppel-like family of zinc-finger transcription factors implicated in cellular development and differentiation. Previous studies from our laboratory indicate that KLF2 inhibits pro-inflammatory activation of monocytic cell lines. However, the role of KLF2 in macrophage activation and function of primary cells remains unknown.
Methods and Results: To gain insights regarding the role of KLF2 in macrophage biology, both gain-of-function and loss-of-function studies were undertaken. For gain-of-function analyses, RAW264.7 cells were infected with empty control virus (Ad-EV) and KLF2 virus (Ad-K2) for 24 hours followed by assessment of key inflammatory targets by quantitative PCR and ELISA. Our studies revealed a marked reduction in both mRNA expression and protein secretion of CD40L, MCP-1, IL-1β, and TNFα. To assess the effect of KLF2 deficiency, we harvested primary peritoneal macrophages from KLF2+/+ and KLF2+/− mice. These cells were cultured for 24 hours, stimulated with LPS (50 ng/ml) overnight, and then assessed for target genes. As expected, the expression of all 4 targets was increased in KLF2+/+; however, this induction was markedly enhanced in KLF2+/− macrophages. Finally, to gain insights regarding the effect of KLF2 deficiency on macrophage function, migration (Transwell) and invasion (Matrigel) assays were performed. We find that KLF2 deficiency augments both macrophage migration (KLF2+/+: 256±8.8% versus KLF2+/−: 380±9.7%, P<5×10−6) and invasion (KLF2+/+: 248±10.6% versus KLF2+/−: 329±10.2%, P<1×10−4) following LPS activation. Finally, our mechanistic studies suggest that the anti-inflammatory effects of KLF2 are mediated, at least in part, by its ability to inhibit the NF-kB pathway.
Conclusion: Our results indicate that KLF2 is novel regulator of macrophage activation. As such, targeting of KLF2 function may be beneficial in preventing a wide spectrum of inflammatory disease such as atherosclerosis.