Neuropeptide Y Has a Protective Role during Murine Retrovirus-Induced Neurological Disease

Abstract

Viral infections in the central nervous system (CNS) can lead to neurological disease either directly by infection of neurons or indirectly through activation of glial cells and production of neurotoxic molecules.Understanding the effects of virus-mediated insults on neuronal responses and neurotrophic support is important in elucidating the underlying mechanisms of viral diseases of the CNS. In the current study, we examined the expression of neurotrophin-and neurotransmitter-related genes during infection of mice with neurovirulent polytropic retrovirus. In this model, virus-induced neuropathogenesis is indirect, as the virus predominantly infects macrophages and microglia and does not productively infect neurons or astrocytes. Virus infection is associated with glial cell activation and the production of proinflammatory cytokines in the CNS. In the current study, we identified increased expression of neuropeptide Y (NPY), a pleiotropic growth factor which can regulate both immune cells and neuronal cells, as a correlate with neurovirulent virus infection. Increased levels of Npy mRNA were consistently associated with neurological disease in multiple strains of mice and were induced only by neurovirulent, not avirulent, virus infection. NPY protein expression was primarily detected in neurons near areas of virus-infected cells. Interestingly, mice deficient in NPY developed neurological disease at a faster rate than wild-type mice, indicating a protective role for NPY. Analysis of NPY-deficient mice indicated that NPY may have multiple mechanisms by which it influences virus-induced neurological disease, including regulating the entry of virus-infected cells into the CNS.

BLT-humanized C57BL/6 Rag2−/−γc−/−CD47−/− mice are resistant to GVHD and develop B- and T-cell immunity to HIV infection

“…Tissues were then processed for immunohistochemistry using the Discovery XT automated processor with a DAPMap kit (Ventana Medical Systems). Organoids were processed as previously described 27 and stained with mouse anti-HIV p24 (M085701; Dako), rabbit anti-Iba1 immunoglobulin G (IgG) (018-19741; Wako), A555-conjugated goat anti-mouse IgG, and A488-conjugated donkey anti-rabbit IgG (Invitrogen). Slides were mounted with ProLong Gold antifade reagent with 4,6 diamidino-2-phenylindole (Invitrogen). )…”

Neuropeptide Y Negatively Influences Monocyte Recruitment to the Central Nervous System during Retrovirus Infection

“…Further, deficiency in NPY significantly increased the incidence and kinetics of retrovirus-mediated neurological disease (14). However, we were unable to determine a specific mechanism for this inhibition, as we saw no significant differences in cell tropism of virus infection, localization of virus within the CNS, astrocyte and microglion activation, or neuronal damage.…”

“…Total RNA was treated with DNase I (Ambion, Austin, TX) for 30 min at 37°C and purified over RNA cleanup columns (Zymo Research) following the manufacturer's instructions. RNA samples were transcribed to cDNA using the iScript reverse transcription kit (Bio-Rad) as previously described (14). Samples that did not undergo reverse transcription were used to verify the lack of DNA contamination.…”

“…We recently found that retrovirus infection in the CNS results in increased production of neuropeptide Y (NPY) by neurons (14). Further, deficiency in NPY significantly increased the incidence and kinetics of retrovirus-mediated neurological disease (14).…”

“…In this model, infection of newborn mice with neurovirulent murine retrovirus Fr98 or BE, a chimeric retrovirus encoding a neurovirulent epitope of the Fr98 envelope protein (11), results in the development of severe neurological disease characterized by repeated seizures, progressive ataxia, and ultimately death (12). The mechanism of neuronal damage is indirect, as these viruses do not productively infect neurons but rather primarily infect microglia in the CNS (13,14). Interestingly, the histological changes associated with Fr98 infection are substantially different from those observed with ecotropic retroviruses, as neither spongiform degeneration nor intracerebral hemorrhages are associated with disease development (15).…”