Curcumin Inhibits Rift Valley Fever Virus Replication in Human Cells

Aarthi Narayanan,Kylene Kehn-Hall,Svetlana Senina,Lindsay Lundberg,Rachel Van Duyne,Irene Guendel,Ravi Das,Alan Baer,Laura Bethel,Michael Turell,Amy Lynn Hartman,Bhaskar Das,Charles Bailey,Fatah Kashanchi

doi:10.1074/jbc.m112.356535

Abstract

Rift Valley fever virus (RVFV) is an arbovirus that is classified as a select agent, an emerging infectious virus, and an agricultural pathogen. Understanding RVFV-host interactions is imperative to the design of novel therapeutics. Here, we report that an infection by the MP-12 strain of RVFV induces phosphorylation of the p65 component of the NFκB cascade. We demonstrate that phosphorylation of p65 (serine 536) involves phosphorylation of IκBα and occurs through the classical NFκB cascade. A unique, low molecular weight complex of the IKK-β subunit can be observed in MP-12-infected cells, which we have labeled IKK-β2. The IKK-β2 complex retains kinase activity and phosphorylates an IκBα substrate. Inhibition of the IKK complex using inhibitors impairs viral replication, thus alluding to the requirement of an active IKK complex to the viral life cycle. Curcumin strongly down-regulates levels of extracellular infectious virus. Our data demonstrated that curcumin binds to and inhibits kinase activity of the IKK-β2 complex in infected cells. Curcumin partially exerts its inhibitory influence on RVFV replication by interfering with IKK-β2-mediated phosphorylation of the viral protein NSs and by altering the cell cycle of treated cells. Curcumin also demonstrated efficacy against ZH501, the fully virulent version of RVFV. Curcumin treatment down-regulated viral replication in the liver of infected animals. Our data point to the possibility that RVFV infection may result in the generation of novel versions of host components (such as IKK-β2) that, by virtue of altered protein interaction and function, qualify as unique therapeutic targets.

Highlights

Rift Valley fever virus is a single-stranded RNA virus that causes disease in humans and livestock
The NF␬B Subunit p65 Is Phosphorylated at Serine 536 in MP-12-infected Cells—Using a reverse-phase protein microarray (RPMA) approach, we demonstrated previously that infection of human small airway lung epithelial cells (HSAECs) with the virulent strain of Rift Valley fever virus (RVFV) (ZH501) causes phosphorylation and activation of multiple signal transduction events including p38 MAPK, JNK, ERK, and their downstream transcription targets including p65 (NF␬B) in the host cell [18]
Specific to the NF␬Bsignaling pathway, RPMA studies indicate that following infection by ZH501 virus, p65 is phosphorylated at serine 536 [18]

Summary

Background

Rift Valley fever virus is a single-stranded RNA virus that causes disease in humans and livestock. Results: Rift Valley fever virus infection activates the host NF␬B signaling cascade. Our data demonstrated that curcumin binds to and inhibits kinase activity of the IKK-␤2 complex in infected cells. Our data point to the possibility that RVFV infection may result in the generation of novel versions of host components (such as IKK-␤2) that, by virtue of altered protein interaction and function, qualify as unique therapeutic targets. We demonstrated previously that inhibition of the host signaling kinase components such as JNK and MEK inhibits viral replication [18] Along these lines, recent publications by our colleagues have provided evidence that regulation of the host factors in the context of RVFV infection is a viable and attractive therapeutic strategy to down-regulate virus replication [26, 27]. Our experiments using the INFARϪ/Ϫ murine model [28, 29] provide preliminary proofof-concept validation that curcumin can down-regulate virus in the livers of infected animals as well, paving the way for further development of novel curcumin-based therapeutic options

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION