Novel Target for Limiting VEGF-A (Vascular Endothelial Growth Factor A)–Induced Vascular Permeability

HomeArteriosclerosis, Thrombosis, and Vascular BiologyVol. 42, No. 10Novel Target for Limiting VEGF-A (Vascular Endothelial Growth Factor A)–Induced Vascular Permeability Free AccessEditorialPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessEditorialPDF/EPUBNovel Target for Limiting VEGF-A (Vascular Endothelial Growth Factor A)–Induced Vascular Permeability Joyce Bischoff Joyce BischoffJoyce Bischoff Correspondence to: Joyce Bischoff, PhD, Karp Family Research Laboratories 12.212, Boston Children’s Hospital, 300 Longwood Ave, Boston, MA 02115. Email E-mail Address: [email protected] https://orcid.org/0000-0002-6367-1974 Vascular Biology Program and Department of Surgery, Boston Children’s Hospital, Boston, MA (J.B.). Department of Surgery, Harvard Medical School, Boston, MA (J.B.). Search for more papers by this author Originally published25 Aug 2022https://doi.org/10.1161/ATVBAHA.122.318105Arteriosclerosis, Thrombosis, and Vascular Biology. 2022;42:1242–1243This article is a commentary on the followingPLCβ2 Promotes VEGF-Induced Vascular PermeabilityOther version(s) of this articleYou are viewing the most recent version of this article. Previous versions: August 25, 2022: Ahead of Print Temporal and spatial control of vascular permeability operates continuously throughout a diverse assortment of vascular beds lining our tissues and organs. Physiological permeability allows passage of essential nutrients and trafficking of immune cells. In pathological settings, vascular permeability can overshoot, often due to excessive VEGF-A (vascular endothelial growth factor A) induced by hypoxic conditions. The increased permeability can impair organ and tissue function dramatically, causing suffering and morbidity.See accompanying article on page 1229Phoenix et al1 for the first time identify PLCβ2 (phospholipase Cβ2) as a robust, positive regulator of VEGF-A triggered vascular permeability. Based on their results from 2 in vivo models, they suggest that limiting PLCβ2 activity transiently, using drugs or other molecular tools, might provide a way to minimize vascular permeability in pathological settings such as acute lung injury2 and cardiac ischemia-reperfusion injury.3In their study, Phoenix et al1 employ in vitro and in vivo models to carefully delineate PLCβ2 from its homolog PLCβ3 (phospholipase Cβ3). The 2 phospholipases, among a family of 13 PLC enzymes, are central to phosphoinositide metabolism as they catalyze the hydrolysis of phosphatidyl inositol 4,5-bisphosphate to generate the potent signaling mediators inositol 1, 4, 5-triphosphate (IP3) and diacylglycerol. Earlier work showed PLCβ3 can negatively regulate VEGF-induced vascular permeability in zebrafish and in mice by decreasing calcium entry into endothelial cells.4 PLCβs are activated by direct interaction with the heterotrimeric G-protein Gαq, with further regulation incurred by phosphatidylinositol composition and distribution within the plasma membrane (for review, see Muralidharan et al5).The first experiment in their study was to assess vascular permeability after intradermal injection of VEGF-A into ears of wild-type, PLCβ2 null, and PLCβ3 null mice. PLCβ2 null animals showed a striking absence of VEGF-A induced permeability. In contrast, basal permeability measured in several different tissues did not differ among the 3 lines of mice. The loss of VEGF-A induced permeability in the absence of PLCβ2 was confirmed in lung endothelial cells from isolated from wild-type, PLCβ2 null, and PLCβ null mice. The lung endothelial cells from PLCβ2 null mice also showed an attenuated release of intracellular calcium over a 1- to 2-second time frame. The authors next extended their findings using more stable telomerase-immortalized human microvascular endothelial cells in which they were able to perform shRNA (short hairpin RNA) knockdown of PLCβ2 versus PLCβ3. shPLCβ2 (short hairpin PLCb3) telomerase-immortalized human microvascular endothelial cells showed dramatically blunted intracellular calcium release and entry of calcium from extracellular milieu (Figure). These results prompted the question—would elimination of PLCβ2 spare mice from injury caused by excessive VEGF-A–induced vascular permeability?Download figureDownload PowerPointFigure. Endothelial PLCβ2 (phospholipase Cβ2) catalyzes hydrolysis of phosphatidyl inositol 4,5-bisphosphate (PIP2) to inositol 1, 4, 5-triphosphate (IP3) and diacylglycerol (DAG). IP3 mediates release of calcium (Ca++) from the intracellular stores in the endoplasmic reticulum and DAG facilitates entry of extracellular calcium, both of which are reduced in PLCβ2 null endothelial cells. Decreased vascular permeability in PLCβ2 null mice supports a positive regulatory role for PLCβ2 in VEGF-A (vascular endothelial growth factor A) stimulated vascular permeability.The first in vivo experiment was to expose mice to hyperoxia followed by return to room air, which stimulated dramatic increases in VEGF-A in the lungs. The lungs of PLCβ2 null animals had reduced vascular permeability, fewer changes in lung morphology, and less weight loss compared to wild-type animals. The second in vivo model was a transient (30 minutes) ligation of the left anterior descending artery to simulate cardiac ischemia-reperfusion injury. Immediately following, vascular permeability was evident in regions adjacent to the ligation site in wild-type mice but to a lesser extent in PLCβ2 null animals. After 10 weeks of recovery, the protection from vascular permeability in the PLCβ2 null animals was associated with significantly smaller infarct sizes. These observations in the lung and the heart strongly point to PLCβ2 as a potential drug target: inhibiting its activity should reduce the vascular permeability caused by excessive and/or prolonged VEGF-A exposure.As the authors discuss, developing such drugs is likely to be challenging because the PLCβ isozymes share conserved substrate binding sites and catalytic mechanisms. Rather than direct inhibition of PLCβ2, it might be possible to target an activation step between VEGF-A and PLCβ2 that is distinct from the activation of PLCβ3. Figure 2 in their paper shows that PLCβ3 null endothelial cells respond to VEGF-A by increasing endothelial permeability, as do wild-type endothelial cells but PLCβ2 null endothelial cells do not. This underscores that VEGF-A/VEGFR (VEGF-receptor) signaling to PLCβ2 is needed to increase permeability but signaling to PLCβ3 is not. All three respond equally to histamine, suggesting G-protein coupled receptor signaling through Gαq is operating. This suggests that a specific target point might reside between VEGFR signaling and PLCβ2 that could be exploited for therapeutic purposes. Or perhaps PLCβ2 has other functions that impact endothelial-endothelial junctions, as has been proposed for PLCβ family members.6 Continued investigations into how PLCβ2 contributes to VEGF-A induced vascular permeability is warranted given the potential to mitigate its pathological effects.Article InformationDisclosures None.FootnotesThe opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.For Disclosures, see page 1243.Correspondence to: Joyce Bischoff, PhD, Karp Family Research Laboratories 12.212, Boston Children’s Hospital, 300 Longwood Ave, Boston, MA 02115. Email joyce.[email protected].harvard.eduReferences1. Phoenix KN, Yue Z, Yue L, Cronin CG, Liang BT, Hoeppner LH, Claffey KP. PLCβ2 promotes VEGF-induced vascular permeability.Arterioscler Thromb Vasc Biol. 2022: 42:1229–1241. doi: 10.1161/ATVBAHA.122.317645LinkGoogle Scholar2. Jones JH, Minshall RD. Endothelial transcytosis in acute lung injury: emerging mechanisms and therapeutic approaches.Front Physiol. 2022; 13:828093. doi: 10.3389/fphys.2022.828093CrossrefMedlineGoogle Scholar3. Hausenloy DJ, Chilian W, Crea F, Davidson SM, Ferdinandy P, Garcia-Dorado D, van Royen N, Schulz R, Heusch G. The coronary circulation in acute myocardial ischaemia/reperfusion injury: a target for cardioprotection.Cardiovasc Res. 2019; 115:1143–1155. doi: 10.1093/cvr/cvy286CrossrefMedlineGoogle Scholar4. Hoeppner LH, Phoenix KN, Clark KJ, Bhattacharya R, Gong X, Sciuto TE, Vohra P, Suresh S, Bhattacharya S, Dvorak AM, et al. Revealing the role of phospholipase Cβ3 in the regulation of VEGF-induced vascular permeability.Blood. 2012; 120:2167–2173. doi: 10.1182/blood-2012-03-417824CrossrefMedlineGoogle Scholar5. Muralidharan K, Van Camp MM, Lyon AM. Structure and regulation of phospholipase Cβ and ε at the membrane.Chem Phys Lipids. 2021; 235:105050. doi: 10.1016/j.chemphyslip.2021.105050CrossrefMedlineGoogle Scholar6. Jackson L, Qifti A, Pearce KM, Scarlata S. Regulation of bifunctional proteins in cells: Lessons from the phospholipase Cβ/G protein pathway.Protein Sci. 2020; 29:1258–1268. doi: 10.1002/pro.3809CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetailsRelated articlesPLCβ2 Promotes VEGF-Induced Vascular PermeabilityKathryn N. Phoenix, et al. Arteriosclerosis, Thrombosis, and Vascular Biology. 2022;42:1229-1241 October 2022Vol 42, Issue 10 Advertisement Article InformationMetrics © 2022 American Heart Association, Inc.https://doi.org/10.1161/ATVBAHA.122.318105PMID: 36004641 Originally publishedAugust 25, 2022 KeywordsphospholipaseEditorialsinositolvascular endothelial growth factor AphosphoinositidePDF download Advertisement SubjectsAngiogenesisGrowth Factors/Cytokines