Nucleoside reverse transcriptase inhibitors (NRTIs) induce proinflammatory cytokines in the CNS via Wnt5a signaling

Abstract

HAART is very effective in suppressing HIV-1 replication in patients. However, patients staying on long-term HAART still develop various HIV-associated neurological disorders, even when the viral load is low. The underlying pathogenic mechanisms are largely unknown. Emerging evidence implicated that persistent neuroinflammation plays an important role in NeuroAIDS. Although residual virus or viral proteins are commonly thought as the causal factors, we are interested in the alternative possibility that HAART critically contributes to the neuroinflammation in the central nervous system (CNS). To test this hypothesis, we have determined the effect of NRTIs on the expression of proinflammatory cytokines in the various CNS regions. Mice (C57Bl/6) were administered with AZT (Zidovudine 100 mg/kg/day), 3TC (Lamivudine 50 mg/kg/day) or D4T (Stavudine 10 mg/kg/day) for 5 days, and cortices, hippocampi and spinal cords were collected for immunoblotting. Our results showed that NRTI administration up-regulated cytokines, including IL-1β, TNF-α and IL-6 in various CNS regions. In addition, we found that NRTIs also up-regulated Wnt5a protein. Importantly, BOX5 attenuated NRTI-induced cytokine up-regulation. These results together suggest that NRTIs up-regulate proinflammatory cytokines via a Wnt5a signaling-dependent mechanism. Our findings may help understand the potential pathogenic mechanisms of HAART-associated NeuroAIDS and design effective adjuvants.

Figure 1

NRTIs up-regulate the expression of inflammatory cytokines in the CNS. Protein levels of cytokine in cortex (a), hippocampus (b) and spinal cord (c) treated with NRTIs for 5 days. Datas presented in graphs are means ± SEM from 5 mice per group *p < 0.05, **p < 0.01, ***p < 0.001vs vehicle.

Figure 2

NRTIs up-regulate Wnt5a in the CNS. Protein levels of Wnt5a in cortex (a), hippocampus (b) and spinal cords (c) treated with NRTIs for 5 days. Datas presented in graphs are means ± SEM from 5 mice per group *p < 0.05,**p < 0.01, ***p < 0.001 vs vehicle. (d) immunohistochemistry staining of Wnt5a in spinal cords from mice treated with NRTIs.

Figure 3

Wnt5a antagonists attenuate NRTIs-induced cytokine up-regulation in the CNS. Protein levels of cytokine in cortex (a), hippocampus (b) and spinal cord (c) treated with NRTIs and BOX5 for 5 days. Datas presented in graphs are means ± SEM from 5 mice per group *p < 0.05, **p < 0.01,***p < 0.001vs vehicle.

Figure 4

BOX5 inhibited the expression of wnt5a in the CNS. Protein levels of Wnt5a in cortex (a), hippocampus (b) and spinal cord (c) treated with NRTIs and BOX5 for 5 days. Datas presented in graphs are means ± SEM from 5 mice per group *p < 0.05, **p < 0.01, ***p < 0.001vs vehicle.

Figure 5

Pathogenetic mechanisms for NRTI-induced neuroAIDS in CNS.