Cyclooxygenase 2 induced by Kaposi's sarcoma-associated herpesvirus early during in vitro infection of target cells plays a role in the maintenance of latent viral gene expression.
Infection of human dermal microvascular endothelial (HMVEC-d) cells and human foreskin fibroblast (HFF) cells in vitro by Kaposi's sarcoma-associated herpesvirus (KSHV) provides an excellent in vitro model system to study viral latency. KSHV infection is characterized by the induction of preexisting host signal cascades; sustained expression of the latency-associated open reading frame 73 (ORF73) (LANA-1), ORF72, and K13 genes; transient expression of a limited number of lytic genes, including the lytic cycle switch ORF50 (replication and transcription activator) gene; and reprogramming of host transcriptional machinery regulating a variety of cellular processes, including several proinflammatory responses. The cyclooxygenase 2 (COX-2) gene was one of the host cell genes that was highly up-regulated at 2 and 4 h postinfection (p.i.) of HMVEC-d and HFF cells (P. P. Naranatt, H. H. Krishnan, S. R. Svojanovsky, C. Bloomer, S. Mathur, and B. Chandran, Cancer Res. 64:72-84, 2004). Since COX-2 is an important mediator of inflammatory and angiogenic responses, here, using real-time PCR, Western blot, and immunofluorescence assays, we characterized the COX-2 stimulation and its role in KSHV infection. KSHV induced a robust COX-2 expression, which reached a maximum at 2 h p.i. in HMVEC-d cells and at 8 h p.i. in HFF cells, and significantly higher levels were continuously detected for up to 72 h p.i. Constitutive COX-1 protein levels were not modulated by KSHV infection. Moderate levels of COX-2 were also induced by UV-irradiated KSHV and by envelope glycoproteins gB and gpK8.1A; however, viral gene expression appears to be essential for the increased COX-2 induction. High levels of prostaglandin E(2) (PGE(2)), a COX-2 product, were released in the culture supernatant medium of infected cells. PGE(2) synthase, catalyzing the biosynthesis of PGE(2), also increased upon infection and inhibition of COX-2 by NS-398, and indomethacin drastically reduced the levels of PGE(2) and PGE(2) synthase. COX-2 inhibition did not affect KSHV binding, internalization of virus, or the trafficking to the infected cell nuclei. However, latent ORF73 gene expression and ORF73 promoter activity were significantly reduced by COX-2 inhibitors, and this inhibition was relieved by exogenous supplementation with PGE(2). In contrast, lytic ORF50 gene expression and ORF50 promoter activity were unaffected. These studies demonstrate that COX-2 and PGE(2) play roles in facilitating latent viral gene expression and the establishment and maintenance of latency and suggest that KSHV has evolved to utilize the inflammatory responses induced during infection of endothelial cells for the maintenance of viral latent gene expression.
Sharma-Walia
Neelam
N
Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA.
Raghu
Hari
H
Sadagopan
Sathish
S
Sivakumar
Ramu
R
Veettil
Mohanan Valiya
MV
Naranatt
Pramod P
PP
Smith
Marilyn M
MM
Chandran
Bala
B
D002460:Cell Line; D051545:Cyclooxygenase 1 / Q000096:biosynthesis; D051546:Cyclooxygenase 2 / Q000096:biosynthesis*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis; D042783:Endothelial Cells / Q000201:enzymology / Q000821:virology; D005347:Fibroblasts / Q000201:enzymology / Q000821:virology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D015967:Gene Expression Regulation, Viral / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D006566:Herpesviridae Infections / Q000201:enzymology*; D019288:Herpesvirus 8, Human / Q000502:physiology*; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D007249:Inflammation / Q000201:enzymology / Q000821:virology; D008565:Membrane Proteins / Q000096:biosynthesis*; D009578:Nitrobenzenes / Q000494:pharmacology; D016366:Open Reading Frames / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D014466:Ultraviolet Rays; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D014759:Viral Envelope Proteins / Q000378:metabolism*; D017735:Virus Latency / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D014779:Virus Replication / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects
D016861:Cyclooxygenase Inhibitors; D008565:Membrane Proteins; D009578:Nitrobenzenes; D013449:Sulfonamides; D014759:Viral Envelope Proteins; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human; D015232:Dinoprostone; D007213:Indomethacin