Substance P enhances HIV-1 infection in human fetal brain cell cultures expressing full-length neurokinin-1 receptor.

The associations between the neurokinin-1 receptor (NK-1R), substance P (SP), and HIV-1 were investigated in neurosphere-derived cultures of microglial-depleted human fetal brain cells (HFBC). Full-length NK-1R was identified in HFBC cultures. SP treatment of the HFBC increased intracellular calcium mobilization and decreased electrical impedance, both of which were blocked by the NK-1R antagonist aprepitant. SP treatment of HIV-1-infected HFBC upregulated HIV-1 expression. These data show that human neural cells grown from neurospheres express functional full length NK-1R that is responsive to SP, and that SP enhanced HIV-1 infection in HBFC.

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.

Prevalence of pain and association with psychiatric symptom severity in perinatally HIV-infected children as compared to controls living in HIV-affected households.

This cross-sectional study evaluated the prevalence of pain and psychiatric symptoms in perinatally HIV-infected children at entry into P1055, a multicenter investigation of the prevalence and severity of psychiatric symptoms in HIV-infected children. Subjects 6-17 years of age and their primary caregivers were recruited from 29 International Maternal Pediatric Adolescent AIDS Clinical Trials sites in the USA and Puerto Rico. A total of 576 children (320 HIV and 256 HIV- children) were enrolled from June 2005 to September 2006. Subject self-reports of pain were measured by the Wong-Baker visual analog scale and Short-Form McGill Pain Questionnaire. Symptomatology for anxiety, depression, and dysthymia was assessed through Symptom Inventory instruments. Caregiver's assessment of their child's pain and psychiatric symptomatology was similarly measured. Logistic regression models were used to evaluate predictors of pain. We found that a higher proportion of HIV-infected than uninfected subjects reported pain in the last two months (41% vs 32%, p=0.04), last two weeks (28% vs 19%, p=0.02), and lasting more than one week (20% vs 11%, p=0.03). Among HIV-infected youth, females (OR=1.53, p=0.09), White race (OR=2.15, p=0.04), and Centers for Disease Control (CDC) Class C (OR=1.83, p=0.04) were significantly more likely to report pain. For all subjects, only 52% of caregivers recognized their child's pain and just 22% were aware that pain affected their child's daily activities. The odds of reported pain in HIV increased with higher symptom severity for generalized anxiety (OR=1.14, p=0.03), major depression (OR=1.15, p=0.03), and dysthymia (OR=1.18, p=0.01). This study underscores the importance of queries concerning pain and emotional stressors in the care of HIV and uninfected children exposed to HIV individuals. The discordance between patient and caregiver reports of pain and its impact on activities of daily living highlights that pain in children is under-recognized and therefore potentially under-treated.

Neurokinin 1 receptor mediates membrane blebbing in HEK293 cells through a Rho/Rho-associated coiled-coil kinase-dependent mechanism.

We have investigated the effect of neurokinin 1 receptor (NK1R) agonists on HEK293 cells transfected with the NK1R receptor. The NK1R receptor mediates dramatic shape changes that include contractions of the membrane cortex resulting in membrane bleb formation. We have found that the cell shape changes correlate with changes in electrical impedance measured in cellular monolayers. The shape and impedance changes were prevented after preincubation with NK1R antagonists aprepitant and L-73060. Although bleb formation usually heralds apoptotic cell death, we have found that NK1R-mediated cellular blebbing does not associate with apoptosis. Preincubation with a cell-permeable derivative of C3 transferase that blocks Rho or with the Rho-associated coiled-coil kinase inhibitor Y27632 completely prevented NK1R-induced shape and impedance changes. Blebbing was also completely inhibited by ML-9, a myosin light chain kinase inhibitor. Furthermore, the phospholipase C inhibitor U73,122 did not interfere with the effect of Substance P (SP) on cellular morphology and cellular impedance but completely blocked SP-induced intracellular calcium increase, indicating that the blebbing is a process independent of intracellular calcium elevations. Blebbing is a protein kinase C-independent process, since the nonselective protein kinase C inhibitor GF109203X did not interfere with SP-induced effects. Based on these results, we provide the first evidence that NK1R receptor-ligand interaction can cause apoptosis-independent cellular blebbing and that this process is mediated by the Rho/Rho-associated coiled-coil kinase pathway.

Substance P (SP) enhances CCL5-induced chemotaxis and intracellular signaling in human monocytes, which express the truncated neurokinin-1 receptor (NK1R).

Substance P (SP) is a potent modulator of monocyte/macrophage function. The SP-preferring receptor neurokinin-1 receptor (NK1R) has two forms: a full-length NK1R (NK1R-F) isoform and a truncated NK1R (NK1R-T) isoform, which lacks the terminal cytoplasmic 96-aa residues. The distribution of these receptor isoforms in human monocytes is not known. We previously identified an interaction among SP, NK1R, and HIV viral strains that use the chemokine receptor CCR5 as a coreceptor, suggesting crosstalk between NK1R and CCR5. The purpose of this study was to determine which form(s) of NK1R are expressed in human peripheral blood monocytes and to determine whether SP affects proinflammatory cellular responses mediated through the CCR5 receptor. Human peripheral blood monocytes were found to express NK1R-T but not NK1R-F. SP interactions with NK1R-T did not mobilize calcium (Ca2+), but SP mobilized Ca2+ when the NK1R-F was transfected into monocytes. However, the NK1R-T was functional in monocytes, as SP enhanced the CCR5 ligand CCL5-elicited Ca2+ mobilization, a response inhibited by the NK1R antagonist aprepitant. SP interactions with the NK1R-T also enhanced CCL5-mediated chemotaxis, which was ERK1/2-dependent. NK1R-T selectively activated ERK2 but increased ERK1 and ERK2 activation by CCL5. Activation of NK1R-T elicited serine phosphorylation of CCR5, indicating that crosstalk between CCL5 and SP may occur at the level of the receptor. Thus, NK1R-T is functional in human monocytes and activates select signaling pathways, and the NK1R-T-mediated enhancement of CCL5 responses does not require the NK1R terminal cytoplasmic domain.

Neurokinin-1 receptor expression and function in human macrophages and brain: perspective on the role in HIV neuropathogenesis.

Substance P (SP) is upregulated in HIV infection in adult men and women, as determined by increased plasma levels. There is a reciprocal and bidirectional relationship between substance P and HIV in HIV-infected monocyte-derived macrophages and cell lines (e.g., THP-1). Substance P up-regulates HIV and HIV up-regulates SP protein expression. Neurokinin-1 receptor (NK1R) antagonists inhibit HIV infectivity through downregulation of the chemokine receptor, CCR5, and downregulation of HIV LTR. Neurokinin-1 receptor is expressed in full-length and truncated forms. The full-length NK1R is capable of signaling, whereas the truncated NK1R primes the chemokine receptor CCR5. Both full-length and truncated NK1R are expressed in several brain regions in human autopsy brains. SP-NK1R interactions have regulatory roles in inflammation and infection. The differential expression of truncated and full-length NK1R has important biological consequences. These include receptor-receptor interaction (e.g., NK1R-CCR5); changes in expression during cell differentiation (e.g., THP-1 cells); and differences in regional tissue distribution (e.g., differences in different brain regions). NK1R-SP receptor pathways are important cell regulatory pathways.

Evidence of human immunodeficiency virus type 1 infection of nestin-positive neural progenitors in archival pediatric brain tissue.

Human immunodeficiency virus type 1 (HIV-1) central nervous system (CNS) infection in children is associated with impaired brain growth and neurodevelopmental delays. Neural progenitors are critical for neurogenesis. Human multipotential neural progenitors grown in culture are permissive for HIV-1 infection, but it is not known if infection of these cells occurs in vivo. Brain tissue from pre-highly active antiretroviral therapy (HAART) era pediatric acquired immunodeficiency syndrome (AIDS) patients was examined for evidence of HIV-1 infection of nestin-positive neural progenitors by in situ hybridization; or after laser microdissection harvest, DNA extraction, and polymerase chain reaction (PCR). HIV-1 or viral DNA was identified in nestin-positive cells in four of seven HIV-1-infected children, suggesting in vivo infection of neural progenitors.

Neural progenitors and HIV-1-associated central nervous system disease in adults and children.

The human immunodeficiency virus type 1 (HIV-1) is a neurotrophic lentivirus that enters and infects the central nervous system (CNS) of adults and children, giving rise to the clinical syndromes of AIDS-dementia complex (ADC) in adults and HIV-1-associated progressive encephalopathy (PE) in pediatric patients. The clinical presentation and progression of neuroAIDS in the developing brain of children is distinct from that seen in adult patients. Neuroimaging, and upon autopsy, neuropathological findings corresponding to clinical disease in pediatric patients include impaired brain growth, reactive gliosis, myelin pallor, calcifications of the basal ganglia, cortical and cerebral atrophy with neuronal loss and ventricular enlargement, and abnormalities of cerebral vasculature. Although there is some overlap with neuropathologic findings in adult patients, ADC in adults is more typically a late development, often complicated by opportunistic infections of the CNS. The neuropathogenesis of ADC and PE is incompletely understood. One population of CNS cells critical for brain development and response to injury and inflammation are neural progenitors cells, and it has therefore been suggested that these cells may be involved in the neuropathogenesis of ADC, and especially PE. This review examines the neurobiology of neural progenitor cells and the possibility that HIV-1 infection of neural progenitors, exposure of neural progenitors to virus, viral products, or progenitor exposure to HIV-1 associated neuroinflammatory substances and neurotoxins might contribute to the neuropathogenesis of AIDS in adults and children. That some of the clinical differences between ADC and PE might, in part, be explained by differences in neural progenitor involvement will also be considered.

Human immunodeficiency virus type 1 infection of human brain-derived progenitor cells.

Although cells of monocytic lineage are the primary source of human immunodeficiency virus type 1 (HIV-1) in the brain, other cell types in the central nervous system, including astrocytes, can harbor a latent or persistent HIV-1 infection. In the present study, we examined whether immature, multipotential human brain-derived progenitor cells (nestin positive) are also permissive for infection. When exposed to IIIB and NL4-3 strains of HIV-1, progenitor cells and progenitor-derived astrocytes became infected, with peak p24 levels of 100 to 500 pg/ml at 3 to 6 days postinfection. After 10 days, virus production was undetectable but could be stimulated by the addition of tumor necrosis factor alpha (TNF-alpha). To bypass limitations to receptor entry, we compared the fate of infection in these cell populations by transfection with the infectious HIV-1 clone, pNL4-3. Again, transfected progenitors and astrocytes produced virus for 7 days but diminished to low levels beyond 8 days posttransfection. During the nonproductive phase, TNF-alpha stimulated virus production from progenitors as late as 5 weeks posttransfection. Astrocytes produced 5- to 20-fold more infectious virus (27 ng of p24/10(6) cells) than progenitors at the peak of 3 days posttransfection. Differentiation of infected progenitors toward an astrocyte phenotype increased virus production to levels consistent with infected astrocytes, suggesting a phenotypic difference in viral replication. Using this cell culture system of multipotential human brain-derived progenitor cells, we provide evidence that progenitor cells may be a reservoir for HIV-1 in the brains of AIDS patients.