Phosphoinositide 3-kinase δ inactivation prevents vitreous-induced activation of AKT/MDM2/p53 and migration of retinal pigment epithelial cells

Abstract

Edited by Xiao-Fan Wang Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that play a critical role in transmitting signals from cellsurface molecules to intracellular protein effectors. Key PI3Ks include PI3K␣, PI3K␤, and PI3K␦, which are regulated by receptors. The signaling pathway comprising the PI3Ks, along with a Ser/Thr kinase (AKT), a proto-oncogene product (mouse double minute (MDM)2), and a tumor suppressor protein (p53), plays an essential role in experimental proliferative vitreoretinopathy (PVR), which is a fibrotic blinding eye disorder. However, which PI3K isoforms are involved in PVR is unknown. A major characteristic of PVR is the formation of epi (or sub)retinal membranes that consist of extracellular matrix and cells, including retinal pigment epithelium (RPE) cells, glial cells, and macrophages. RPE cells are considered key players in PVR pathogenesis. Using immunoblotting and immunofluorescence analyses, we herein provide the evidence that PI3K␦ is highly expressed in human RPEs when it is primarily expressed in leukocytes. We also found that PI3K␦ inactivation through two approaches, CRISPR/Cas9-mediated depletion and a PI3K␦specific inhibitor (idelalisib), not only blocks vitreous-induced activation of AKT and MDM2 but also abrogates a vitreousstimulated decrease in p53. Furthermore, we demonstrate that PI3K␦ inactivation prevents vitreous-induced proliferation, migration, and contraction of human RPEs. These results suggest that PI3K␦ may represent a potential therapeutic target for RPE-related eye diseases, including PVR.

Chalcomoracin Prevents Vitreous-Induced Activation of AKT and Migration of Retinal Pigment Epithelial Cells

“…PDGF-BB has been reported to be capble to induce the underlying pathways of Erk, p38, JNK activation in PVR [37], on the other hand, TGFβ induces epithelial mesenchymal transition (EMT) [38,39] in RPEs. Thus, many signaling pathways are activated in PVR pathogenesis, of which especially Akt/MDM2/p53 among those signals is hyperactive in the virtreal environment [29,40]. Our data was clearly evident that CMR at 5 μM completely blocked vitreous-induced activation of Akt, and p53 attenuation, however, whether it can suppress the activation of Erk, p38 or JNK induced by vitreous remains unknown.…”

Chalcomoracin prevents vitreous‐induced activation of AKT and migration of retinal pigment epithelial cells

“…38 Idelalisib at 1 μmol/L completely inhibited vitreous-induced activation of Akt, but it did not block Erk activation at its 10 μmol/L concentration, 38 suggesting that idelalisib specifically blocked vitreous-stimulated activation of Akt. 38,39 Given that the formation of PVR is a complicated process, here we revealed for the first time that, as a natural compound, ). Therefore, we hypothesize that CMR can inhibit PVR, which is closely related to proliferation and migration of RPEs.…”

“… 38 Idelalisib at 1 μmol/L completely inhibited vitreous‐induced activation of Akt, but it did not block Erk activation at its 10 μmol/L concentration, 38 suggesting that idelalisib specifically blocked vitreous‐stimulated activation of Akt. 38 , 39 Given that the formation of PVR is a complicated process, here we revealed for the first time that, as a natural compound, CMR has the advantage of effective, multi‐target and low toxicity, in terms of blocking vitreous‐induced cellular responses contributes to PVR. CMR has been shown as a broad spectrum of biological activities, but there has not yet been any thorough investigation into the molecular mechanisms of CMR involved in different diseases except human reproductive system cancer.…”

Normal vitreous promotes angiogenesis via activation of Axl

“…However, the role of vitreous in the ocular pathology is still unclear. Based on our previous findings 7 we hypothesize the vitreous contains some soluble factors that can induce pathological angiogenesis from retina.…”

“…4 Recently, several papers have been published describing the angiogenic and inflammatory activity of vitreous obtained from proliferative diabetic retinopathy patients. 5 However, our previous findings showed that vitreous from healthy animals enhances the signaling pathway of phosphoinositide 3-kinase (PI3K)/Akt, cell proliferation and migration of human pigment retinal epithelial cells, 6,7 and the PI3K/Akt signaling pathway plays a critical role in angiogenesis. 8 In addition, tandem mass spectrometry showed that there are some pro-angiogenic proteins in the vitreous, and the majority of vitreal proteins detected are intracellular proteins, some of which may originate from retina.…”