Substance P enhances tissue factor release from granulocyte-macrophage colony-stimulating factor-dependent macrophages via the p22phox/β-arrestin 2/Rho A signaling pathway

In Silico Drug Repurposing by Structural Alteration after Induced Fit: Discovery of a Candidate Agent for Recovery of Nucleotide Excision Repair in Xeroderma Pigmentosum Group D Mutant (R683W)

Xeroderma pigmentosum complementation group D (XPD) is a UV-sensitive syndrome and a rare incurable genetic disease which is caused by the genetic mutation of the excision repair cross-complementation group 2 gene (ERCC2). Patients who harbor only XPD R683W mutant protein develop severe photosensitivity and progressive neurological symptoms. Cultured cells derived from patients with XPD (XPD R683W cells) demonstrate a reduced nucleotide excision repair (NER) ability. We hope to ameliorate clinical symptoms if we can identify candidate agents that would aid recovery of the cells' NER ability. To investigate such candidates, we created in silico methods of drug repurposing (in silico DR), a strategy that utilizes the recovery of ATP-binding in the XPD R683W protein after the induced fit. We chose 4E1RCat and aprepitant as the candidates for our in silico DR, and evaluated them by using the UV-induced unscheduled DNA synthesis (UDS) assay to verify the recovery of NER in XPD R683W cells. UDS values of the cells improved about 1.4-1.7 times after 4E1RCat treatment compared with solvent-only controls; aprepitant showed no positive effect. In this study, therefore, we succeeded in finding the candidate agent 4E1RCat for XPD R683W. We also demonstrated that our in silico DR method is a cost-effective approach for drug candidate discovery.

TRIM28/TIF1β and Fli-1 negatively regulate peroxynitrite generation via DUOX2 to decrease the shedding of membrane-bound fractalkine in human macrophages after exposure to substance P

The chemokine fractalkine is synthesized as a membrane-bound protein, but studies have shown that serum levels of soluble fractalkine are elevated in inflammatory and autoimmune diseases. Patients with autoimmune diseases also have increased serum levels of neuropeptide substance P (SP). The shedding activity of the ADAM family is induced by peroxynitrite, but that of SP is unclear. Treatment of human macrophages with SP upregulated levels of membrane-bound fractalkine. Interestingly, small interfering RNA (siRNA) for DUOX2 further increased membrane-bound fractalkine but decreased soluble fractalkine compared with cells treated with SP alone. SP induced nitric oxide 2/inducible nitric oxide synthase (NOS2/iNOS) mRNA and increased levels of nitrotyrosine, a biomarker of peroxynitrite, whereas transfection with DUOX2 siRNA blunted upregulation of nitrotyrosine. Most importantly, N(ω)-nitro-L-arginine methyl ester (L-NAME, a nitric oxide synthase inhibitor) decreased protein levels of nitrotyrosine and concomitantly increased expression of membrane-bound fractalkine after exposure to SP. As for the signaling pathway of TGFβ1 (an inhibitor of iNOS mRNA expression), silencing of RNA for TAK-1 upregulated membrane-bound fractalkine, but silencing of RNA for the Smad family did not. Interfering RNA of transcription factor specificity protein 1 (Sp1) upregulated protein levels of TGFβ1/LAP. Most importantly, double transfection with siRNA for Sp1 and TRIM28/TIF1βor Fli-1 led to a significant increase in TGFβ1/LAP levels and a corresponding reduction of NOS2/iNOS, which inhibited the shedding of membrane-bound fractalkine. In conclusion, TRIM28/TIF1β and Fli-1 negatively regulate TGFβ1 expression to upregulate the generation of peroxynitrite, leading to increased shedding of membrane-bound fractalkine induced by SP.

Di-(2-Ethylhexyl) Phthalate Promotes Release of Tissue Factor-Bearing Microparticles From Macrophages via the TGFβ1/Smad/PAI-1 Signaling Pathway

BACKGROUND

Plasminogen activator inhibitor type 1 promotes formation of endothelial microparticles with procoagulant activity. However, it remains unclear whether di-(2-ethylhexyl) phthalate, a peroxisome proliferator-activated receptor α agonist, influences microparticle formation.

MATERIALS AND METHODS

The effect of di-(2-ethylhexyl) phthalate on release of tissue factor-bearing microparticles was investigated using human M1 macrophages.

RESULTS

Exposure of M1 macrophages to di-(2-ethylhexyl) phthalate significantly upregulated expression of plasminogen activator inhibitor type 1, whereas incubation of macrophages with small interfering RNA for peroxisome proliferator-activated receptor α attenuated it. Di-(2-ethylhexyl) phthalate significantly increased the tissue factor protein level in culture supernatants of M1 macrophages, but not M2 macrophages. After purification of proteins by centrifugal filtration, western blotting detected 2 high molecular weight bands of tissue factor-bearing microparticles in culture supernatants of M1 macrophages. The upper band showed binding to factor VIIa and tissue factor pathway inhibitor, unlike the lower band. This suggested heterogeneity of the procoagulant activity of tissue factor-bearing microparticles, presumably dependent upon encryption/decryption of tissue factor. Phosphatidylserine contributes to tissue factor decryption, and western blotting revealed that the density of phosphatidylserine was reduced in the upper tissue factor band compared with the lower band. Di-(2-ethylhexyl) phthalate also upregulated transforming growth factor-β1 protein production by M1 macrophages. Moreover, silencing of Smad2, Smad3 or Smad4 attenuated plasminogen activator inhibitor type 1 expression and tissue factor-release from macrophages after di-(2-ethylhexyl) phthalate stimulation.

CONCLUSIONS

Di-(2-ethylhexyl) phthalate promotes formation of tissue factor-bearing microparticles in human M1 macrophages via the transforming growth factor-β1/Smad/ plasminogen activator inhibitor type 1 signaling pathway.

Transcription factor specificity protein 1 modulates TGFβ1/Smad signaling to negatively regulate SIGIRR expression by human M1 macrophages stimulated with substance P

The stimuli inducing expression of single immunoglobulin IL-1-related receptor (SIGIRR) and the relevant regulatory mechanisms are not well defined. Transforming growth factor β1 (TGFβ1) delays internalization of neurokinin-1 receptor (NK1R) and subsequently enhances cellular signaling. This study investigated the effect of TGFβ1 on SIGIRR protein production by human M1 macrophages in response to stimulation with substance P (SP). SP caused upregulation of SIGIRR expression in a concentration-dependent manner, whereas aprepitant (an NK1R inhibitor) blunted this response. Silencing p38γMAPK or TAK-1 partially attenuated the response to SP stimulation, while TGFβ1/2/3 siRNA dramatically diminished it. SP induced much greater SIGIRR protein production than either lipopolysaccharide (a TLR4 agonist) or resiquimod (a TLR7/8 agonist). Unexpectedly, silencing of transcription factor specificity protein 1 (Sp1) led to significant upregulation of SIGIRR expression after SP stimulation, while KLF2 siRNA only partially enhanced it and Fli-1 siRNA reduced it. SP also upregulated TGFβ1 expression, along with a corresponding increase of SIGIRR protein, whereas silencing TGFβ1/2/3 blunted these responses. Sp1 siRNA or mithramycin (a gene-selective Sp1 inhibitor) significantly enhanced the expression of TGFβ1 and SIGIRR by macrophages after SP stimulation. Importantly, this effect of Sp1 siRNA on TGFβ1 and SIGIRR was blunted by siRNA for Smad2, Smad3, or Smad4, but not by TAK-1 siRNA. Next, we investigated the influence of transcription factor cross-talk on SIGIRR expression in response to SP. Co-transfection of macrophages with Sp1 siRNA and C/EBPβ or TIF1β siRNA attenuated the upregulation of SIGIRR by SP, while a combination of Sp1 siRNA and Fli-1 siRNA dramatically diminished it. In conclusion, TGFβ1 may be an intermediary between SP/NK1R activation and SIGIRR expression in Sp1 siRNA-transfected macrophages. In addition, Sp1 modulates TGFβ1/Smad signaling and negatively regulates SIGIRR protein production by macrophages after SP stimulation.

Cross-talk between the transcription factor Sp1 and C/EBPβ modulates TGFβ1 production to negatively regulate the expression of chemokine RANTES

RANTES is a key chemokine for atherosclerosis, and obesity is associated with progression of atherosclerosis. Substance P (SP) increases glucose uptake and accumulation of lipids in adipocytes, and SP may upregulate RANTES expression. This study investigated the mechanism of RANTES expression by human M1 macrophages stimulated with SP.

SP upregulated RANTES protein expression, whereas aprepitant (an NK1R antagonist) blunted this response. Pretreatment of macrophages with BIRB796 (a combined p38γ/p38δ inhibitor) led to a significant decrease of RANTES expression. Next, we investigated the effect of several NK1R internalization factors on RANTES expression, including GRK2, β-arrestin 2, dynamin, ROCK, and TGFβ1. Exposure of macrophages to SP upregulated TGFβ1 expression. Silencing of β-arrestin 2 or GRK2 significantly enhanced the RANTES protein level after stimulation by SP, whereas TGFβ1/2/3 siRNA or dynasore (a dynamin inhibitor) decreased RANTES and Y-27632 (a ROCK inhibitor) had no effect. Surprisingly, silencing of transcription factor specificity protein 1 (Sp1) or inhibition of Sp1 activity by mithramycin led to significant upregulation of TGFβ1 protein and corresponding enhancement of RANTES expression (by ELISA or western blotting), whereas siRNA for C/EBPβ attenuated expression of both TGFβ1 and RANTES. Next, we investigated transcriptional cross-talk among Sp1 and C/EBPβ, TIF1β, or Fli-1 in relation to RANTES expression. Compared with TIF1β or Fli-1 siRNA, C/EBPβ siRNA showed significantly stronger inhibition of RANTES production by Sp1 siRNA-transfected macrophages after stimulation with SP.

In conclusion, transcription factor Sp1 engages in cross-talk with C/EBPβ and modulates TGFβ1 production to negatively regulate RANTES expression in macrophages stimulated with SP.

In conclusion, cross-talk between the transcription factor Sp1 and C/EBPβ modulates TGFβ1 production to negatively regulate expression of the atherogenic chemokine RANTES in SP-stimulated macrophages, while RANTES is upregulated by SP via the p38γδMAPK/C/EBPβ/TGFβ1 signaling pathway.

β-Arrestin 1 has an essential role in neurokinin-1 receptor-mediated glioblastoma cell proliferation and G2/M phase transition

Glioblastoma is the most common malignant brain tumor and has a poor prognosis. Tachykinin receptor neurokinin-1 (NK1R) is a promising target in glioblastoma therapy because of its overexpression in human glioblastoma. NK1R agonists promote glioblastoma cell growth, whereas NK1R antagonists efficiently inhibit cell growth both in vitro and in vivo However, the molecular mechanisms involved in these effects are incompletely understood. β-Arrestins (ARRBs) serve as scaffold proteins and adapters to mediate intracellular signal transduction. Here we show that the ARRB1-mediated signaling pathway is essential for NK1-mediated glioblastoma cell proliferation. ARRB1 knockdown significantly inhibited NK1-mediated glioblastoma cell proliferation and induced G₂/M phase cell cycle arrest. ARRB1 knockdown cells showed remarkable down-regulation of CDC25C/CDK1/cyclin B1 activity. We also demonstrated that ARRB1 mediated prolonged phosphorylation of ERK1/2 and Akt in glioblastoma cells induced by NK1R activation. ERK1/2 and Akt phosphorylation are involved in regulating CDC25C/CDK1/cyclin B1 activity. The lack of long-term ERK1/2 and Akt activation in ARRB1 knockdown cells was at least partly responsible for the delayed cell cycle progression and proliferation. Moreover, we found that ARRB1-mediated ERK1/2 and Akt phosphorylation regulated the transcriptional activity of both NF-κB and AP-1, which were involved in cyclin B1 expression. ARRB1 deficiency increased the sensitivity of glioblastoma cells to the treatment of NK1R antagonists. Taken together, our results suggest that ARRB1 plays an essential role in NK1R-mediated cell proliferation and G₂/M transition in glioblastoma cells. Interference with ARRB1-mediated signaling via NK1R may have potential significance for therapeutic strategies targeting glioblastoma.

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.