Endogenous IL-32 controls cytokine and HIV-1 production.
IL-32, a proinflammatory cytokine that activates the p38MAPK and NF-kappaB pathways, induces other cytokines, for example, IL-1beta, IL-6, and TNF-alpha. This study investigated the role of endogenous IL-32 in HIV-1 infection by reducing IL-32 with small interfering (si)RNA in freshly infected PBMC and in the latently infected U1 macrophage cell line. When PBMC were pretreated with siRNA to IL-32 (siIL-32), IL-6, IFN-gamma, and TNF-alpha were reduced by 57, 51, and 36%, respectively, compared with scrambled siRNA. Cotransfection of NF-kappaB and AP-1 reporter constructs with siIL-32 decreased DNA binding of these transcription factors by 42 and 46%, respectively. Cytokine protein array analysis revealed that the inhibitory activity of siIL-32 primarily targeted Th1 and proinflammatory cytokines and chemokines, e.g., MIP-1alpha/beta. Unexpectedly, HIV-1 production (as measured by p24) increased 4-fold in these same PBMC when endogenous IL-32 was reduced. Because IFN-gamma was lower in siIL-32-treated PBMC, we blocked IFN-gamma bioactivity, which enhanced the augmentation of p24 by siIL-32. Furthermore, siIL-32 reduced the natural ligands of the HIV-1 coreceptors CCR5 (MIP-1alpha/beta and RANTES) and CXCR4 (SDF-1). Inhibition of endogenous IL-32 in U1 macrophages also increased HIV-1. When rhIL-32gamma was added to these cells, p24 levels fell by 72%; however, in the same cultures IFN-alpha increased 4-fold. Blockade of IFN-alpha/beta bioactivity in IL-32gamma-stimulated U1 cells revealed that IFN-alpha conveys the anti-HIV-1 effect of rhIL-32gamma. In summary, depletion of endogenous IL-32 reduced the levels of Th1 and proinflammatory cytokines but paradoxically increased p24, proposing IL-32 as a natural inhibitor of HIV-1.
Department of Medicine, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Marcel F
MF
Nold
Claudia A
CA
Nold-Petry
Gregory B
GB
Pott
Jarod A
JA
Zepp
Milene T
MT
Saavedra
Soo-Hyun
SH
Kim
Charles A
CA
Dinarello
D019380:Anti-HIV Agents / Q000378:metabolism*; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis* / Q000235:genetics; D004247:DNA / Q000378:metabolism; D016655:HIV Core Protein p24 / Q000096:biosynthesis; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D007378:Interleukins / Q000172:deficiency / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D018808:Transcription Factor AP-1 / Q000378:metabolism; D015854:Up-Regulation
D019380:Anti-HIV Agents; D016207:Cytokines; D016655:HIV Core Protein p24; D007378:Interleukins; D016328:NF-kappa B; D034741:RNA, Small Interfering; D018808:Transcription Factor AP-1; C514799:p24 protein, Human Immunodeficiency Virus Type 1; D004247:DNA