Expression profiling suggests microglial impairment in human immunodeficiency virus neuropathogenesis.

OBJECTIVE: CD16+ /CD163+ macrophages (MΦs) and microglia accumulate in the brains of patients with human immunodeficiency virus (HIV) encephalitis (HIVE), a neuropathological correlate of the most severe form of HIV-associated neurocognitive disorders, HIV-associated dementia. Recently, we found that some parenchymal microglia in brain of HIV+ subjects without encephalitis (HIV/noE) but with varying degrees of neurocognitive impairment express CD16 and CD163, even in the absence of detectable virus production. To further our understanding of microglial activation in HIV, we investigated expression of specific genes by profiling parenchymal microglia from archival brain tissue of patients with HIVE and HIV/noE, and HIV- controls. METHODS: Single-population microarray analyses were performed on ∼2,500 laser capture microdissected CD163+ , CD16+ , or CD68+ MΦs/microglia per case, using terminal continuation RNA amplification and a custom-designed array platform. RESULTS: Several classes of microglial transcripts in HIVE and HIV/noE were altered, relative to HIV- subjects, including factors related to cell stress, immune activation, and apoptosis. Additionally, several neurotrophic factors were reduced in HIV infection, suggesting an additional mechanism of neuropathogenesis. The majority of transcripts altered in HIVE displayed intermediate changes in HIV/noE. INTERPRETATION: Our results support the notion that microglia contribute to the maintenance of brain homeostasis and their potential loss of function in the context of chronic inflammation contributes to neuropathogenesis. Furthermore, they indicate the utility of profiling MΦs/microglia to increase our understanding of microglia function, as well as to ascertain alterations in specific pathways, genes, and potentially, encoded proteins that may be amenable to targeted treatment modalities in diseases affecting the brain. Ann Neurol 2018;83:406-417.

Substance P inhibits natural killer cell cytotoxicity through the neurokinin-1 receptor.

SP is a potent neuroimmunomodulator that functions through ligating members of the neurokinin receptor family, one of which, NK1R, is widely expressed in immune cells. As in humans, circulating SP levels are increased in pathologic states associated with impairment of NK cell functions, such as depression and HIV infection, we hypothesized that SP has a direct, inhibitory effect upon NK cells. We have studied a clonal human NK cell line (YTS) as well as ex vivo human NK cells and have determined that truncated and full-length NK1R isoforms are expressed in and SP bound by ex vivo NK cells and the YTS NK cell line. Incubation of YTS cells with 10⁻6 M SP and ex vivo NK cells with 10⁻5 M SP inhibited cytotoxic ability by ∼20% and reduced degranulation. This inhibitory effect upon cytotoxicity was partially prevented by the NK1R antagonist CP96,345. The treatment of YTS or ex vivo NK cells with SP neither down-modulated NCR expression nor affected triggering receptor-induced NF-κB activation. Preincubation of YTS cells with SP, however, did abbreviate the typically prolonged intracellular calcium increase induced by target cell engagement and reduced triggering receptor-induced pERK. Thus, SP has the potential to regulate NK cell functions and acts downstream from neurokinin receptors to modulate NK cell activation signaling. This mechanism may contribute to impairment of NK cell function in certain disease states associated with increased circulating SP. Antagonism of this system may present an opportunity to augment NK cell function therapeutically in selected human diseases.