1. College of Pharmacy & Medical Research Center, Chungbuk National University, Cheongju, Chungbuk 28160, Korea;
2. Department of Dental Hygiene, Gwangyang Health Sciences University, Gwnagyang, Jeonnam 57764, Korea;
3. Department of Molecular Biology, Dankook University, Yongin, Gyeonggi 16890, Korea;
4. Stanley Brain Research Laboratory, Stanley Medical Research Institute, 9800 Medical Center Drive, Rockville, MD 20850, USA;
5. Department of Bioscience and Biotechnology, Konkuk University, Seoul 05029, Korea.
*These authors contributed equally to this work.
Interleukin-32 (IL-32) is a multifaceted cytokine that promotes inflammation and regulates vascular endothelial cell behavior. Although some IL-32 isoforms have been reported to contribute to vascular inflammation and atherosclerosis, the functional role of IL-32α in vascular inflammation and atherogenesis has not been studied.
Methods: IL-32α function was assessed in cells with transient IL-32α overexpression or treated with recombinant human IL-32α by western blotting and mRNA expression analysis. Vascular smooth muscle cell (VSMC) proliferation and migration was examined by BrdU incorporation and wound healing assays, respectively. In addition, the participation of IL-32α on vascular inflammation, arterial wall thickening, and atherosclerosis in vivo was monitored in human IL-32α transgenic (hIL-32α-Tg) mice with or without ApoE knockout (ApoE-/-/hIL-32α-Tg).
Results: Our analyses showed that IL-32α suppresses genes involved in the inflammatory and immune responses and cell proliferation, and by limiting matrix metalloproteinase (MMP) function. In vivo, administration of hIL-32α inhibited vascular inflammation and atherosclerosis in hIL-32α-Tg and ApoE-/-/hIL-32α-Tg mice. Subsequent microarray and in silico analysis also revealed a marked decreased in inflammatory gene expression in hIL-32α-Tg mice. Collectively, our studies demonstrated that IL-32α upregulates the atheroprotective genes Timp3 and Reck by downregulating microRNA-205 through regulation of the Rprd2-Dgcr8/Ddx5-Dicer1 biogenesis pathway.
Conclusion: Our findings provide the first direct evidence that IL-32α is an anti-inflammatory and anti-atherogenic cytokine that may be useful as a diagnostic and therapeutic protein in atherosclerosis.
Keywords: Interleukin 32, Timp3, Reck, Vascular inflammation, Atherosclerosis.