Ritchie Centre, Monash Institute of Medical Research, Monash University, 27-31 Wright Street, Clayton, VIC 3168, Australia
Center for Cardiovascular Research, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, United States
Istituto di Biostrutture e Bioimmagini, Consiglio Nazionale delle Ricerce, Centro Interuniversitario di Ricerca sui Peptidi Bioattivi, 80134 Naples, Italy
Department of Pharmacy, University of Naples Federico II, 80134 Naples, Italy
ArisGen SA, 1228 Plan-les-Ouates, Switzerland
Department of Internal Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States
Department of Medicine, University of Colorado Denver, Aurora, CO 80045, United States
Department of Pathology, University of Colorado Denver, Aurora, CO 80045, United States
Radboud University Medical Center, 6500 HB Nijmegen, Netherlands
Pulmonary and Critical Care Medicine Division, Molecular Medicine Research Building, Virginia Commonwealth University, Broad Street, Richmond, VA 23298, United States
References: Not available.
IL-32 Promotes Angiogenesis
IL-32 is a multifaceted cytokine with a role in infections, autoimmune diseases, and cancer, and it exerts diverse functions, including aggravation of inflammation and inhibition of virus propagation. We previously identified IL-32 as a critical regulator of endothelial cell (EC) functions, and we now reveal that IL-32 also possesses angiogenic properties. The hyperproliferative ECs of human pulmonary arterial hypertension and glioblastoma multiforme exhibited a markedly increased abundance of IL-32, and, significantly, the cytokine colocalized with integrin alpha v beta(3). Vascular endothelial growth factor (VEGF) receptor blockade, which resulted in EC hyperproliferation, increased IL-32 three-fold. Small interfering RNA-mediated silencing of IL-32 negated the 58% proliferation of ECs that occurred within 24 h in scrambled-transfected controls. Reduction of IL-32 neither affected apoptosis (insignificant changes in Bak-1, Bcl-2, Bcl-x(L), lactate dehydrogenase, annexin V, and propidium iodide) nor VEGF or TGF-beta levels, but siIL-32-transfected adult and neonatal ECs produced up to 61% less NO, IL-8, and matrix metalloproteinase-9, and up to 3-fold more activin A and endostatin. In coculture-based angiogenesis assays, IL-32 gamma dose-dependently increased tube formation up to 3-fold; an alpha v beta(3) inhibitor prevented this activity and reduced IL-32 gamma-induced IL-8 by 85%. In matrigel plugs loaded with IL-32 gamma, VEGF, or vehicle and injected into live mice, we observed the anticipated VEGF-induced increase in neocapillarization (8-fold versus vehicle), but unexpectedly, IL-32 gamma was equally angiogenic. A second signal such as IFN-gamma was required to render cells responsive to exogenous IL-32 gamma; importantly, this was confirmed using a completely synthetic preparation of IL-32 gamma. In summary, we add angiogenic properties that are mediated by integrin alpha v beta(3) but VEGF-independent to the portfolio of IL-32, implicating a role for this versatile cytokine in pulmonary arterial hypertension and neoplastic diseases.