Differential Angiogenic Properties of Lithium Chloride In Vitro and In Vivo

Abstract

Wnt/β-catenin signaling induced by the Norrin/Frizzled-4 pathway has been shown to improve capillary repair following oxygen induced retinopathy (OIR) in the mouse, a model for retinopathy of prematurity. Here we investigated if treatment with the monovalent cation lithium that has been shown to augment Wnt/β-catenin signaling in vitro and in vivo has similar effects. In cultured human microvascular endothelial cells, LiCl as well as SB 216763, another small molecule that activates Wnt/β-catenin signaling, induced proliferation, survival and migration, which are all common parameters for angiogenic properties in vitro. Moreover, treatment with both agents caused an increase in the levels of β-catenin and their translocation to nuclei while quercetin, an inhibitor of Wnt/β-catenin signaling, completely blocked the effects of LiCl on proliferation. In mice with OIR, intraperitonal or intravitreal treatment with LiCl markedly increased the retinal levels of β-catenin, but did not improve capillary repair. In contrast, repair was significantly improved following intravitreal treatment with Norrin. The effects of LiCl on HDMEC in vitro have minor relevance for OIR in vivo, and the influence of the Norrin/Frizzled-4 pathway on capillary repair in OIR is not reproducible upon enhancing Wnt/β-catenin signaling by LiCl treatment strongly indicating the presence of additional and essential mechanisms.

In Vitro Human Umbilical Vein Endothelial Cells Response to Ionic Dissolution Products from Lithium-Containing 45S5 Bioactive Glass

“…Similar results have been recently obtained in our laboratory when incubating glass-ceramic scaffolds derived from the glass 45S5.5Li in M199 medium. It is important to note that the concentration of Li + released from the previously mentioned biomaterials is below the reported reference values at which cytotoxic effects are apparent (5–25 mmol) [ 18 , 24 , 46 , 47 , 48 ]. However, Bruckner et al observed a higher release of Li + (5.5 mmol) from microparticles (<38 µm or 300–500 µm) of the glass 45S5 with 12.2% in moles of Li 2 O incubated for 72 h in Tris buffer [ 33 ].…”

“…Recent experimental results have shown that Li + stimulates the in vitro secretion of growth factors with proangiogenic activity and participates in angiogenesis in vivo [ 24 ]. It has also been shown that Li + induces the proliferation, migration, and survival of endothelial cells by activating the Wnt/β-catenin canonical pathway [ 24 , 25 , 26 , 27 ]. These properties would constitute the rational base for the use of Li + in biomaterials feasible for application in regenerative medicine and in the engineering of tissues with a high degree of vascularization such as bone tissue.…”

Pharmacologic Activation of Wnt Signaling by Lithium Normalizes Retinal Vasculature in a Murine Model of Familial Exudative Vitreoretinopathy

“…Proangiogenic effects of lithium were demonstrated in our endothelial cell culture and also in previous studies in embryonic vessels in vivo and in endothelial cells in vitro. 63,64 Our data suggest that lithium's vascular effects were likely mediated primarily through activation of the Wnt signaling pathway, by inhibiting the secondary Wnt signaling complex containing GSK3b, thus stabilizing the downstream factor b-catenin to eventually promote vascular formation. However, it is not clear whether potential Wnt/GSK3-independent effects of lithium may also be at work, including those through inositol depletion, 65 bone morphogenetic protein (BMP)-2 signaling, 66 transcription factor 7-like 2 gene RNA splicing, 67 or mitogenactivated protein (MAP) extracellular signal-related kinase (ERK) kinase (MEK)-ERK pathway.…”

Bmp4-Msx1 signaling and Osr2 control tooth organogenesis through antagonistic regulation of secreted Wnt antagonists

“…We first tested intraperitoneal injection of LiCl, a simple salt that is known to activate Wnt signaling through inhibition of GSK3β (Klein and Melton, 1996; Song et al, 2009; Zeilbeck et al, 2014), in the pregnant mice bearing Bmp4 ncko/ncko mutant embryos. As control, we treated mice with NaCl, a structurally similar salt but without an effect on GSK3β activity.…”

“…Although LiCl is known to activate β-catenin-mediated canonical Wnt signaling through inhibition of GSK3β (Klein and Melton, 1996; Song et al, 2009; Zeilbeck et al, 2014), the effect of LiCl treatment in utero is likely not limited to Wnt signaling since GSK3β has many endogenous substrates, in addition to β-catenin, and affects multiple signaling pathways and transcription factors (for recent reviews, Beurel et al, 2015; Takahashi-Yanaga et al, 2013). To directly test whether increased expression of secreted Wnt antagonists in the developing tooth mesenchyme is responsible for the mandibular molar developmental arrest in the Bmp4 ncko/ncko mutant embryos, we injected IIIC3a, a small molecule that binds to the Wnt co-receptors Lrp5/6 to block inhibition of canonical Wnt signaling by Dkk1 or Dkk2, but itself does not cause activation of Wnt signaling in the absence of Wnt ligands (Li et al, 2012), into the pregnant mice bearing Bmp4 ncko/ncko mutant embryos from gestational days 12 to 14.…”