Nitrosative damage during retrovirus infection-induced neuropathic pain

Abstract

BackgroundPeripheral neuropathy is currently the most common neurological complication in HIV-infected individuals, occurring in 35–50% of patients undergoing combination anti-retroviral therapy. Data have shown that distal symmetric polyneuropathy develops in mice by 6 weeks following infection with the LP-BM5 retrovirus mixture. Previous work from our laboratory has demonstrated that glial cells modulate antiviral T-cell effector responses through the programmed death (PD)-1: PD-L1 pathway, thereby limiting the deleterious consequences of unrestrained neuroinflammation.MethodsUsing the MouseMet electronic von Frey system, we assessed hind-paw mechanical hypersensitivity in LP-BM5-infected wild-type (WT) and PD-1 KO animals. Using multi-color flow cytometry, we quantitatively assessed cellular infiltration and microglial activation. Using real-time RT-PCR, we assessed viral load, expression of IFN-γ, iNOS, and MHC class II. Using western blotting, we measured protein nitrosylation within the lumbar spinal cord (LSC) and dorsal root ganglion (DRG). Histochemical staining was performed to analyze the presence of CD3, ionized calcium binding adaptor molecule (Iba)-1, MHCII, nitrotyrosine, isolectin B4 (IB4) binding, and neurofilament 200 (NF200). Statistical analyses were carried out using graphpad prism.ResultsHind-paw mechanical hypersensitivity observed in LP-BM5-infected animals was associated with significantly increased lymphocyte infiltration into the spinal cord and DRG. We also observed elevated expression of IFN-γ (in LSC and DRG) and MHC II (on resident microglia in LSC). We detected elevated levels of 3-nitrotyrosine within the LSC and DRG of LP-BM5-infected animals, an indicator of nitric oxide (NO)-induced protein damage. Moreover, we observed 3-nitrotyrosine in both small (IB4+) and large (NF200+) DRG sensory neurons. Additionally, infected PD-1 KO animals displayed significantly greater mechanical hypersensitivity than WT or uninfected mice at 4 weeks post-infection (p.i.). Accelerated onset of hind-paw hypersensitivity in PD-1 KO animals was associated with significantly increased infiltration of CD4+ and CD8+ T lymphocytes, macrophages, and microglial activation at early time points. Importantly, we also observed elevated levels of 3-nitrotyrosine and iNOS in infected PD-1 KO animals when compared with WT animals.ConclusionsResults reported here connect peripheral immune cell infiltration and reactive gliosis with nitrosative damage. These data may help elucidate how retroviral infection-induced neuroinflammatory networks contribute to nerve damage and neuropathic pain.

Chronic Pain in HIV

“…28 The infiltration of lymphocytes into DRG and spinal cord has been demonstrated in an LP-BM5, a murine retroviral isolate, infected murine AIDS (MAID) model. 39 Specifically, these immune cells released redox-active species into DRG neurons, resulting in oxidative damage and increased mechanosensitivity of the hindpaw. 39 The role of macrophages in neuropathic pain is further emphasized by demonstration of reduced mechanical hypersensitivity and Wallerian degeneration in rats after depletion of macrophages with dichloromethylene diphosphonate-containing liposomes.…”

“…39 Specifically, these immune cells released redox-active species into DRG neurons, resulting in oxidative damage and increased mechanosensitivity of the hindpaw. 39 The role of macrophages in neuropathic pain is further emphasized by demonstration of reduced mechanical hypersensitivity and Wallerian degeneration in rats after depletion of macrophages with dichloromethylene diphosphonate-containing liposomes. 40 Other animal models limiting macrophage recruitment have also demonstrated a corresponding reduction in neuronal degeneration and hyperalgesia.…”

Restriction of H1N1 influenza virus infection by selenium nanoparticles loaded with ribavirin via resisting caspase-3 apoptotic pathway

“…GraphPad Prism 5.0 software (GraphPad Software, Inc., La Jolla, CA, USA) was used for data analysis. 38 Two-tailed Student's t-test and a one-way analysis of variance were used to evaluate the significance of the data. Differences were considered statistically significant at P,0.05 (*) or P,0.01 (**).…”

Glial Cell Expression of PD-L1

“…In this review, we primarily discuss findings from various murine models. We have previously shown that PD-1 KO animals displayed significantly greater mechanical hypersensitivity than wild type mice during chronic murine retroviral (LP-BM5) infection, which was associated with significantly increased infiltration of T-lymphocytes, macrophages, and microglial activation [46]. In MCMV-induced brain infection there is chronic neuroinflammation, which persists within the post-encephalitic brain even in the absence of detectable viral antigen [2].…”