Oroxylin A Inhibits Kaposi'S Sarcoma-Associated Herpes Virus (Kshv) Vil-6-Mediated Lymphatic Reprogramming Of Vascular Endothelial Cells Through Modulating Ppar Gamma/Prox1 Axis

Background and purpose Kaposi's sarcoma-associated herpes virus (KSHV) vIL-6 is sufficient to induce lymphatic reprogramming of vascular endothelial cells, which is a key event in Kaposi's sarcoma (KS) development. This study was aimed to investigate the effect of Chinese herb oroxylin A on lymphatic reprogramming and neovascularization by KSHV vIL-6 in vitro and in vivo. Methods The lymphatic-phenotype endothelial cell line was generated by lentiviral KSHV vIL-6 infection. Cell viability and apoptosis were determined by MTT assay or flow cytometry with annexin V/propidium iodide staining. Migration, invasion, and neovascularization of the vIL-6-expressing lymphatic-phenotype endothelial cells were determined by wound healing assay, transwell chamber assay, microtubule formation assay, and chick chorioallantoic membrane assay, respectively. Quantitative polymerase chain reaction and Western blot analysis were used to test the expression of Prox1, VEGFR3, podoplanin, LYVE-1, and PPAR gamma in cells. Co-localization of Prox1 and PPAR gamma was determined by immunofluorescence. Ubiquitination of Prox1 was detected by in vivo ubiquitination assay. Results The lymphatic-phenotype endothelial cell line expressing KSHV vIL-6 was successfully generated. Oroxylin A induced cellular invasion abrogation, apoptosis induction, and neovascularization inhibition of the vIL-6-expressing endothelial cells. Mechanically, oroxylin A elevated PPAR gamma expression, which in turn interacted with and facilitated Prox1 to undergo ubiquitinational degradation, and subsequently leads to VEGFR3, LYVE-1, and podoplanin reduction. Conclusion Through modulating PPAR gamma/Prox1 axis, oroxylin A inhibits lymphatic reprogramming and neovascularization of KSHV vIL-6. Thus, oroxylin A may serve as a candidate for the treatment of KS as well as other aggressive angiomas.