Tetrahydrobiopterin (BH4) deficiency is associated with augmented inflammation and microvascular degeneration in the retina

Abstract

BackgroundTetrahydrobiopterin (BH4) is an essential cofactor in multiple metabolic processes and plays an essential role in maintaining the inflammatory and neurovascular homeostasis. In this study, we have investigated the deleterious effects of BH4 deficiency on retinal vasculature during development.Methods hph-1 mice, which display deficiency in BH4 synthesis, were used to characterize the inflammatory effects and the integrity of retinal microvasculature. BH4 levels in retinas from hph-1 and wild type (WT) mice were measured by LC-MS/MS. Retinal microvascular area and microglial cells number were quantified in hph-1 and WT mice at different ages. Retinal expression of pro-inflammatory, anti-angiogenic, and neuronal-derived factors was analyzed by qPCR. BH4 supplementation was evaluated in vitro, ex-vivo, and in vivo models.ResultsOur findings demonstrated that BH4 levels in the retina from hph-1 mice were significantly lower by ~ 90% at all ages analyzed compared to WT mice. Juvenile hph-1 mice showed iris atrophy, persistent fetal vasculature, significant increase in the number of microglial cells (p < 0.01), as well as a marked degeneration of the retinal microvasculature. Retinal microvascular alterations in juvenile hph-1 mice were associated with a decreased expression in Norrin (0.2-fold) and its receptor Frizzled-4 (FZD4; 0.51-fold), as well as with an augmented expression of pro-inflammatory factors such as IL-6 (3.2-fold), NRLP-3 (4.4-fold), IL-1β (8.6-fold), and the anti-angiogenic factor thrombospondin-1 (TSP-1; 17.5-fold). We found that TSP-1 derived from activated microglial cells is a factor responsible of inducing microvascular degeneration, but BH4 supplementation markedly prevented hyperoxia-induced microglial activation in vitro and microvascular injury in an ex-vivo model of microvascular angiogenesis and an in vivo model of oxygen-induced retinopathy (OIR).ConclusionOur findings reveal that BH4 is a key cofactor in regulating the expression of inflammatory and anti-angiogenic factors that play an important function in the maintenance of retinal microvasculature.Electronic supplementary materialThe online version of this article (10.1186/s12974-017-0955-x) contains supplementary material, which is available to authorized users.

Antenatal IL-1-dependent inflammation persists postnatally and causes retinal and sub-retinal vasculopathy in progeny

“…The detection threshold was established to reduce artefacts and a semi-quantitative comparison of vascular density was performed. Iba-1 positive (Iba1 + ) cells were counted using the ImageJ software in the central retina at Pt1 and in the mid-periphery at Pt15 and 30, as reported 45 .…”

The Median Eminence, A New Oligodendrogenic Niche in the Adult Mouse Brain

“…Consistently, our in vitro and in vivo data suggest that astrocytic TSP1 plays a negative regulator of the oligodendrogenic fate of ME-NSCs both as an intrinsic and an extrinsic factor. Notably, TSP1 staining in the brain appears widely and diffusely, suggesting that there might be another source than just the astrocytes, likely neurons ( Tyzack et al., 2014 ) and activated microglia ( Rivera et al., 2017 ), which are highly abundant under neuroinflammation. In this study, LSKL, which blocks the binding of TSP1 and the large latent TGF-β complex, antagonized the effect of TSP1, suggesting that the effect of TSP1 is mediated by TGF-β.…”

Mesenchymal Stromal Cells Promote Retinal Vascular Repair by Modulating Sema3E and IL-17A in a Model of Ischemic Retinopathy

“…Mice eyes were collected and processed for retinal flat-mounts as previous published studies ( Sitaras et al, 2015 ; Rivera et al, 2017b ). Briefly, eyes were fixed in 4% paraformaldehyde for 1 h and then, retinas were isolated and incubated overnight at 4°C in a solution containing 1% Triton X-100-1 mM CaCl 2 /phosphate-buffered saline (PBS) and TRITC-conjugated lectin endothelial cell marker Bandeiraea simplicifolia (1:100; Sigma-Aldrich, St. Louis, MO, United States).…”