Benzo(a)pyrene in Cigarette Smoke Enhances HIV-1 Replication through NF-\u03baB Activation via CYP-Mediated Oxidative Stress Pathway

Sabina Ranjit,Santosh Kumar,Sunitha Kodidela,Namita Sinha

doi:10.1038/s41598-018-28500-z

Sabina Ranjit, Santosh Kumar + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-28500-z

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Abstract

Smoking aggravates HIV-1 pathogenesis and leads to decreased responses to antiretroviral therapy. In this study, we aim to find a molecular mechanism that would explain smoking-induced HIV-1 replication. Benzo(a)pyrene (BaP), a major carcinogen in cigarette, requires metabolic activation through cytochrome P450s (CYPs) to exert its toxic effects. We hypothesized that CYP-mediated BaP metabolism generates reactive oxygen species (ROS), and the resultant oxidative stress aggravates HIV-1 replication. As expected, we observed ~3 to 4-fold increase in HIV-1 replication in U1 cells and human primary macrophages after chronic BaP exposure. We also observed ~30-fold increase in the expression of CYP1A1 at mRNA level, ~2.5-fold increase in its enzymatic activity as well as elevated ROS and cytotoxicity in U1 cells. The knock-down of the CYP1A1 gene using siRNA and treatment with selective CYP inhibitors and antioxidants significantly reduced HIV-1 replication. Further, we observed a nuclear translocation of NF-κB subunits (p50 and p65) after chronic BaP exposure, which was reduced by treatment with siRNA and antioxidants/CYP inhibitors. Suppression of NF-κB pathway using specific NF-κB inhibitors also significantly reduced HIV-1 replication. Altogether, our results suggest that BaP enhances HIV-1 replication in macrophages by a CYP-mediated oxidative stress pathway followed by the NF-κB pathway.

Highlights

Of the 5000 compounds that are present in CSC, polyaryl hydrocarbons (PAHs) are a class of carcinogenic compounds that are implicated by several studies for their potential to induce oxidative stress[10,11,12]
A 10-fold lower concentration of BaP (10 nM) did not have any significant effect on the viral replication. We confirmed this result in HIV-1-infected human primary macrophages, in which, BaP (100 nM) showed an approximately 3-fold increase in HIV-1 replication (Fig. 1B)
The current report reveals a novel mechanism for BaP-mediated HIV-1 replication in monocyte-derived macrophages in vitro

Summary

Introduction

Of the 5000 compounds that are present in CSC, polyaryl hydrocarbons (PAHs) are a class of carcinogenic compounds that are implicated by several studies for their potential to induce oxidative stress[10,11,12]. Oxidative stress is implicated in enhanced replication of HIV-1 via the activation of redox sensitive nuclear transcription factor Kappa- B (NF-κB)[25,26,27,28]. The activated NF-κB proteins induce the transcription of HIV-1 structural genes by binding to the enhancer region of long terminal repeat (LTR) on HIV-1 DNA, that contains NF-κB binding sites[37]. Whether smoking/tobacco mediated oxidative stress via CYP pathways causes the nuclear trafficking of NF-κB and resultant HIV-1 replication, is yet to be examined. We examined the potential role of CYP-mediated oxidative stress and subsequent HIV-1 replication via the NF-κB pathway by an important tobacco constituent, BaP, in HIV-1-infected macrophages. HIV-1-infected macrophages cross the blood-brain-barrier (BBB) and infect CNS cells such as perivascular macrophages, microglia, and to some extent astrocytes, which eventually cause HIV-1-associated neurocognitive disorders[41,42]

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