The Potential of IL-19 As a Therapeutic Anti-inflammatory and Angiogenic Cytokine

Abstract

Our lab has recently shown that IL-19 is expressed in angiogenic ECs, opening the possibility for its use as a medicine to increase perfusion in patients with PAD. The first aim of the current study is to show IL-19’s ability to increase perfusion in vivo using C57BL/6 wild type and IL-19 KO mice in the hindlimb ischemia (HLI) model. Wild-type mice injected with 10ng/g/day of rmIL-19 after being subject to hindlimb ischemia showed significantly greater levels of perfusion than PBS injected littermates. Immunohistochemistry of harvested gastrocnemius muscle showed a greater level of capillary density in IL-19 injected mice as well. IL-19-/- mice also showed a slower recovery of perfusion in a ligated limb in addition to less CD31 positive cells in gastrocnemius muscle when compared to C57BL/6 wild type mice. IL-19 -/- mice also showed increased perfusion when injected with rmIL-19. The second aim of the study is to show more precisely if IL-19 increases angiogenesis by increasing angiogenic cytokine production, polarizing macrophage phenotype, or by influencing angiogenic and anti-angiogenic factors. Spleen, serum, and bone marrow derived macrophage (BMDM) from mouse models used in Aim 1 showed increased levels of angiogenic cytokines, decreased anti-angiogenic cytokines, and markers of M2 macrophage polarization when IL-19 was injected i.p. or present genetically. The third aim of the study examines whether or not IL-19 can increase perfusion within an atherosclerotic background. It also addresses whether IL-19 can both simultaneously reduce atherosclerosis and increase perfusion. This aim also uses mice lacking LDLR-/- genes to further evaluate these questions. LDLR-/- mice fed a high fat diet for 12 weeks underwent HLI and had perfusion levels measured using Doppler imaging in addition to four weeks of 10ng/g/day of IL-19 or PBS injections. Upon sacrifice mice also had their aortas harvested and stained for plaque measurement. This experiment seeks to demonstrate if IL-19 can increase perfusion on an atherosclerotic background. Additionally, a second set of experiments addresses if LDLR-/- mice injected with recombinant mouse IL-19 (rmIL-19) or PBS for 16 weeks on a HFD in addition to HLI being performed at week 12 showed decreased levels of plaque and increased levels of hindlimb perfusion. These experiments seek to demonstrate if IL-19 can simultaneously reduce atherosclerosis while increasing perfusion. A third set of experiments attempts to evaluate the hypothesis that double knock out mice (DKO) lacking both LDLR and IL-19 genes will have increased plaque after being fed a HFD for 16 weeks. These aims all support the overall hypothesis that IL-19 can increase angiogenesis while additionally proving to be anti-inflammatory and anti-atherogenic in vivo