Sergei Spitsin

Reduction of soluble CD163, substance P, programmed death 1 and inflammatory markers: phase 1B trial of aprepitant in HIV-1-infected adults.

Objective:We evaluated safety, antiviral, immunomodulatory and anti-inflammatory properties of aprepitant – a neurokinin 1 receptor antagonist. Design:Phase IB randomized, placebo-controlled, double-blinded study. Methods:Eighteen patients were randomized (nine to aprepitant and nine to placebo). The patients received once-daily treatment (375 mg aprepitant or placebo by oral administration) for 2 weeks and were followed off drug for 4 weeks. Results:There were no significant changes in the plasma viremia or CD4+ T cells during the dosing period. Aprepitant treatment was associated with significant decreases of median within patient change in percentages of CD4+ T cells expressing programmed death 1 (−4.8%; P = 0.04), plasma substance P (−34.0 pg/ml; P = 0.05) and soluble CD163 (−563 ng/ml; P = 0.02), with no significant changes in the placebo arm. Mean peak aprepitant plasma concentration on day 14 was 7.6 ± 3.1 &mgr;g/ml. The use of aprepitant was associated with moderate increases in total cholesterol, low-density lipoprotein and high-density lipoprotein (median change = +31 mg/dl, P = 0.01; +26 mg/dl, P = 0.02; +3 mg/dl, P = 0.02, respectively). Conclusion:Aprepitant was safe and well tolerated. At the dose used in this proof-of-concept phase IB study, aprepitant did not show a significant antiviral activity. Aprepitant-treated patients had decreased numbers of CD4+ programmed death 1-positive cells and decreased plasma levels of substance P and soluble CD163, suggesting that blockade of the neurokinin 1 receptor pathway has a role in modulating monocyte activation in HIV infection. Prospective studies in virologically-suppressed individuals are warranted to evaluate the immunomodulatory properties of aprepitant. Exposures exceeding those attained in this trial are more likely to elicit clinical benefit.

Adjuvant therapies for HIV‐associated neurocognitive disorders

HIV‐associated neurocognitive disorder (HAND) is a frequent and heterogeneous complication of HIV, affecting nearly 50% of infected individuals in the combined antiretroviral therapy (cART) era. This is a particularly devastating statistic because the diagnosis of HAND confers an increased risk of HIV‐associated morbidity and mortality in affected patients. While cART is helpful in the treatment of the more severe forms of HAND, there is a therapeutic gap in the milder forms of HAND, where cART is less effective. Multiple adjuvant therapies with various mechanisms of action have been studied (N‐methyl D‐aspartate [NMDA]‐receptor antagonists, MAO‐B inhibitors, tetracycline‐class antibiotics, and others), but none have shown a clear positive effect in HAND. While this lack of efficacy may be because the appropriate therapeutic targets have not yet been determined, we aimed to discuss that study results may also influenced by clinical trial design.

Programmed Death 1 Receptor Changes Ex Vivo in HIV-Infected Adults following Initiation of Highly Active Antiretroviral Therapy

ABSTRACT This study investigates the short-term effects of highly active antiretroviral therapy (HAART) on programmed death 1 receptor (PD-1) expression and lymphocyte function. We compared lymphocytes from human immunodeficiency virus (HIV)-infected adults prior to the initiation of HAART with lymphocytes from the same subjects following 2 months of treatment. Short-term HAART resulted in a moderate increase in the expression of PD-1 on both CD4+ and CD8+ T cells; yet, there was still a significant reduction in viral load and recovery of CD4+ T cells. After 2 months of HAART, lymphocytes from the subjects had a reduction in lymphoproliferative responses to phytohemagglutinin (PHA) and an increased response to the Candida recall antigen and the HIV antigen p24 compared to pretreatment lymphocytes. PHA-stimulated peripheral blood mononuclear cells (PBMCs) from samples obtained 2 months after HAART produced higher levels of Th-1 cytokines (gamma interferon [IFN-γ] and tumor necrosis factor alpha[TNF-α]) than the levels observed for samples taken before treatment was initiated. There were no significant changes in the proinflammatory cytokine interleukin-2 (IL-2) or Th-2 cytokines (IL-4, IL-5, and IL-10) in the corresponding samples. Ex vivo PD-1 blockade significantly augmented PHA-induced lymphoproliferation as well as the levels of Th-1 cytokines and to a lesser extent the levels of Th-2 cytokines in PBMC cultures. The ability to downregulate PD-1 expression may be important in enhancing immune recovery in HIV infection.

The Selective Serotonin Reuptake Inhibitor Citalopram Decreases Human Immunodeficiency Virus Receptor and Coreceptor Expression in Immune Cells.

BACKGROUND This study investigated whether the selective serotonin reuptake inhibitor (SSRI) citalopram downregulates the expression of the human immunodeficiency virus (HIV) receptor cluster of differentiation 4 (CD4) and coreceptors chemokine receptor type 5 and chemokine-related receptor type 4 (CCR5 and CXCR4) on peripheral blood mononuclear cells (PBMCs) and macrophages ex vivo as a potential mechanism of reducing susceptibility to HIV infection. METHODS The sample included 150 participants 18-58 years old (59% women, 65% African American, 61% with depression). Monocyte-depleted PBMCs were treated with phytohemagglutinin for 72 hours and then cultured in the presence of interleukin-2 with vehicle control or the SSRI (10(-6) mol/L) for 2 hours. To generate monocyte-derived macrophages, monocytes were cultured for 7 days, after which either vehicle control or SSRI (10(-6) mol/L) was added for 2 hours. RNA was collected from both cell types, and messenger RNA expression of CD4, CCR5, and CXCR4 was measured by real-time polymerase chain reaction. RESULTS In PBMCs, SSRI treatment decreased expression of CD4 (p = .009), CCR5 (p = .008), and CXCR4 (p < .0001). In monocyte-derived macrophages, SSRI treatment decreased expression of CD4 (p < .0001) and CXCR4 (p = .0003), but not CCR5 (p = .71). The suppressive effects of the SSRI on receptor expression did not differ as a function of depression diagnosis or depressive symptom severity. CONCLUSIONS Treatment with the SSRI at a physiologic dose decreased CD4, CCR5, and CXCR4 expression on PBMCs and macrophages ex vivo. These findings suggest that SSRI treatment, independent of depression status, downregulates HIV receptor and coreceptor expression and may reduce susceptibility of immune cells to HIV infection and decrease inflammation. If clinical trials confirm the present findings, ultimately there may be a role for using SSRI treatment adjunctively in HIV and acquired immunodeficiency syndrome.

Substance P–mediated chemokine production promotes monocyte migration

The neuropeptide SP has physiologic and pathophysiologic roles in CNS and peripheral tissues and is involved in crosstalk between nervous and immune systems in various conditions, including HIV and SIV infection. Increased SP levels were demonstrated in plasma of HIV+ individuals as well as in the CNS of SIV‐infected, nonhuman primates. SP increases HIV infection in macrophages through interaction with its receptor, NK1R. The SP effect on immune system is both pro‐ and anti‐inflammatory and includes up‐regulation of a number of cytokines and cell receptors. The main goal of this study was to determine whether there is interplay between monocyte exposure to SP and recruitment into sites of inflammation. We now demonstrate that exposure of either human macrophages or PBMCs to SP leads to increased production of chemokines, including MCP‐1, for which expression is limited to cells of the myeloid lineage. This effect is inhibited by the NK1R antagonist, aprepitant. Exposure to conditioned medium derived from SP‐treated PBMCs resulted in increased monocyte migration through semipermeable membranes and an in vitro human BBB model. Monocyte migration was blocked by anti–MCP‐1 antibodies. Our results suggest that increased SP levels associated with HIV and other inflammatory conditions may contribute to increased monocyte migration into the CNS and other tissues through a MCP‐1–dependent mechanism.

Expression of substance P, neurokinin-1 receptor and immune markers in the brains of individuals with HIV-associated neuropathology.

The tachykinin neuropeptide substance P (SP) has an important signaling role in both the nervous and the immune systems. Two naturally occurring variants of the neurokinin-1 receptor (NK1R) mediate the effects of SP, full-length receptor (NK1R-F) and a truncated form (NK1R-T) that lacks 96 amino acid residues at the C-terminus. We previously reported decreased expression of the NK1R-F in the CNS of HIV-positive individuals in comparison to HIV-negative control subjects. There were no differences in the expression of the NK1R-T in the same groups. In the current study, we quantified the expressions of SP precursor mRNA preprotachykinin (TAC1), NK1R (full and truncated forms), viral load (HIV-gag) and several proinflammatory and immune markers (CD4, CCR5, CXCR4, fractalkine, IL-6, IL-10, CCL2, CCL20 and CD163) in the frontal cortex of autopsied brains from HIV-1-positive individuals with or without HIV-associated neuropathology. The expressions of SP and, to lesser extent, NK1R-F were decreased while the expressions of CXCR4, CCR5 and CCL2 were increased in CNS of individuals with HIV-associated neuropathology. There was no change in HIV loads associated with neuropathology; however, we found a positive correlation between viral loads and the expression of haptoglobin-hemoglobin scavenger receptor CD163. An analysis of CSF from corresponding samples demonstrated an increase in proinflammatory markers (CCL2 MIP-1α and MIP-1β) associated with neuropathology. Although our data confirm the overall inflammatory nature of HIV-associated neuropathology, we observed a decrease in the expression of SP and NK1R-F, which is also associated with other forms of neuroinflammation.

Modeling and Simulation Approach to Support Dosing and Study Design Requirements for Treating HIV-Related Neuropsychiatric Disease with the NK1-R Antagonist Aprepitant

Psychiatric illness is common in HIV-infected patients and underlines the importance for screening not only for cognitive impairment but also for co-morbid mental disease. The rationale for combining immunomodulatory neurokinin- 1 receptor (NK1-R) antagonists with combined antiretroviral therapy (cART) is based on multimodal pharmacologic mechanisms. The NK1-R antagonist aprepitants potential utility as a drug for depression is complicated by >99.9% protein binding and both enzyme inhibition and induction of CYP3A4. A population-based PK model developed from a pilot Phase 1B trial in 19 HIV-infected patients (125 or 250 mg/d aprepitant for 2 weeks) was modified to account for enzyme induction and impact of an exposure enhancer on CYP3A4 metabolism. Likelihood of clinical success in depression was assessed based on achievement of target trough plasma concentration and evaluated using Monte Carlo simulation. Scenarios were generated for varying daily dose (375, 625, 750 and 875 mg), pharmacokinetic variability, exposure enhancement (EE), duration (2 and 6 months) and sample size (n=12 and 24/arm). Daily dosing of ≥ 625 mg with EE yielded desirable troughs (based on in vitro infectivity experiments) of > 2.65 ug/mL for the majority of virtual patients simulated. Results are dependent on the degree of exposure enhancement and extent of enzyme induction. Actual threshold exposure requirements for aprepitant in HIV-associated depression are unknown though preclinical evidence supports trough levels > 2.65 ug/mL. If 100% NK1r blockage is necessary for efficacy, doses of 875 mg (625 mg with EE) or higher may be required. The benefit of aprepitant on innate immunity(natural killer cells) and absence of negative effects onex vivo neutrophil chemotaxis alleviates concerns regarding drug dependent inhibition (DDI)-mediated infection risk.

Analog of Somatostatin Vapreotide Exhibits Biological Effects in vitro via Interaction with Neurokinin-1 Receptor

Objectives: Vapreotide, a synthetic analog of somatostatin, has analgesic activity most likely mediated through the blockade of neurokinin-1 receptor (NK1R), the substance P (SP)-preferring receptor. The ability of vapreotide to interfere with other biological effects of SP has yet to be investigated. Methods: We studied the ability of vapreotide to antagonize NK1R in three different cell types: immortalized U373MG human astrocytoma cells, human monocyte-derived macrophages (MDM) and a human embryonic kidney cell line, HEK293. Both U373MG and MDM express endogenous NK1R while HEK293 cells, which normally do not express NK1R, are stably transformed to express human NK1R (HEK293-NK1R). Results: Vapreotide attenuates SP-triggered intracellular calcium increases and nuclear factor-κB activation in a dose-dependent manner. Vapreotide also inhibits SP-induced interleukin-8 and monocyte chemotactic protein-1 production in HEK293-NK1R and U373MG cell lines. Vapreotide inhibits HIV-1 infection of human MDM in vitro, an effect that is reversible by SP pretreatment. Conclusions: Our findings indicate that vapreotide has NK1R antagonist activity and may have a potential application as a therapeutic intervention in HIV-1 infection.

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.

Truncation of neurokinin‐1 receptor—Negative regulation of substance P signaling

Substance P (SP) is a tachykinin peptide, which triggers intracellular signaling in the nervous and immune systems, as well as, other local and systemic events. The interaction between SP and its receptor, neurokinin‐1 receptor (NK1R), results in major downstream cellular actions, which include changes in calcium fluxes, ERK, and p21‐activated kinase phosphorylation and NFκB activation. Two naturally occurring variants of the NK1R, the full‐length, 407 aa receptor (NK1R‐F) and the truncated, 311 aa isoform (NK1R‐T), mediate the actions of SP. Receptor truncation partially disrupts signaling motifs of the carboxyl tail, a critical site for mediating NK1R signaling, resulting in a “less‐efficient” receptor. Although NK1R‐F is the predominant isoform in the central and peripheral nervous systems, NK1R‐T is expressed in several tissues and cells, which include monocytes, NK cells, and T‐cells. The SP binding domain is not affected by truncation and this site is identical in both NK1R receptor isoforms. However, while cells expressing NK1R‐F respond to nanomolar concentrations of SP, monocyte and macrophage activation, mediated through NK1R‐T, requires micromolar concentrations of SP in order to elicit signaling responses. Elevated plasma levels of SP are associated with increased inflammatory responses and NK1R antagonists reduce inflammation and cytokine production in vivo. This mini review presents and discusses the novel hypothesis that the expression of NK1R‐T on immune system cells prevents immune activation in a milieu, which usually contains low concentrations of SP and, thus, maintains immune homeostasis. In contrast, in the activated neuronal microenvironment, when SP levels reach the threshold at tissue sites, SP promotes immune activation and modulates monocyte/macrophage polarization.