Kaposi's sarcoma-associated herpesvirus induces sustained levels of vascular endothelial growth factors A and C early during in vitro infection of human microvascular dermal endothelial cells: biological implications.
Kaposi's sarcoma (KS), a vascular tumor associated with human immunodeficiency virus type 1 infection, is characterized by spindle-shaped endothelial cells, inflammatory cells, cytokines, growth and angiogenic factors, and angiogenesis. KS spindle cells are believed to be of the lymphatic endothelial cell (LEC) type. Kaposi's sarcoma-associated herpesvirus (KSHV, or human herpesvirus 8) is etiologically linked to KS, and in vitro KSHV infection of primary human dermal microvascular endothelial cells (HMVEC-d) is characterized by the induction of preexisting host signal cascades, sustained expression of latency-associated genes, transient expression of a limited number of lytic genes, sustained induction of NF-kappaB and several cytokines, and growth and angiogenic factors. KSHV induced robust vascular endothelial growth factor A (VEGF-A) and VEGF-C gene expression as early as 30 min postinfection (p.i.) in serum-starved HMVEC-d, which was sustained throughout the observation period of 72 h p.i. Significant amounts of VEGF-A and -C were also detected in the culture supernatant of infected cells. VEGF-A and -C were also induced by UV-inactivated KSHV and envelope glycoprotein gpK8.1A, thus suggesting a role for virus entry stages in the early induction of VEGF and requirement of KSHV viral gene expression for sustained induction. Exogenous addition of VEGF-A and -C increased KSHV DNA entry into target cells and moderately increased latent ORF73 and lytic ORF50 promoter activation and gene expression. KSHV infection also induced the expression of lymphatic markers Prox-1 and podoplanin as early as 8 h p.i., and a paracrine effect was seen in the neighboring uninfected cells. Similar observations were also made in the pure blood endothelial cell (BEC)-TIME cells, thus suggesting that commitment to the LEC phenotype is induced early during KSHV infection of blood endothelial cells. Treatment with VEGF-C alone also induced Prox-1 expression in the BEC-TIME cells. Collectively, these studies show that the in vitro microenvironments of KSHV-infected endothelial cells are enriched, with VEGF-A and -C molecules playing key roles in KSHV biology, such as increased infection and gene expression, as well as in angiogenesis and lymphangiogenesis, thus recapitulating the microenvironment of early KS lesions.
Sivakumar
Ramu
R
Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA.
Sharma-Walia
Neelam
N
Raghu
Hari
H
Veettil
Mohanan Valiya
MV
Sadagopan
Sathish
S
Bottero
Virginie
V
Varga
Laszlo
L
Levine
Rita
R
Chandran
Bala
B
D002196:Capillaries; D002460:Cell Line; D004730:Endothelium, Vascular / Q000378:metabolism / Q000821:virology*; D015870:Gene Expression / Q000187:drug effects; D015967:Gene Expression Regulation, Viral; D019288:Herpesvirus 8, Human / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012867:Skin / Q000098:blood supply / Q000378:metabolism / Q000821:virology*; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D042582:Vascular Endothelial Growth Factor C / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D000098551:Prospero-Related Homeobox 1 Protein; D000098853:Podoplanin
D018398:Homeodomain Proteins; D008562:Membrane Glycoproteins; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; D042582:Vascular Endothelial Growth Factor C; D000098551:Prospero-Related Homeobox 1 Protein; C117468:PDPN protein, human; D000098853:Podoplanin