Reactive oxygen species generation by mast cells in response to substance P: a NK1-receptor-mediated event

Role of substance P in renal injury during DOCA-salt hypertension

Substance P (SP), a neurokinin-1 receptor (NK-1R) agonist, is mainly produced and stored in primary sensory nerves and, upon its release, participates in cardiovascular and renal functional regulation. This study tests the hypothesis that activation of the NK-1Rs by SP occurs during hypertension induced by deoxycorticosterone (DOCA)-salt treatment, which contributes to renal injury in this model. C57BL/6 mice were subjected to uninephrectomy and DOCA-salt treatment in the presence or absence of administration of selective NK-1 antagonists, L-733,060 (20 mg/kg·d, ip) or RP-67580 (8 mg/kg·d, ip). Five weeks after the treatment, mean arterial pressure determined by the telemetry system increased in DOCA-salt mice but without difference between NK-1R antagonist-treated or NK-1R antagonist-untreated DOCA-salt groups. Plasma SP levels were increased in DOCA-salt compared with control mice (P < 0.05). Renal hypertrophy and increased urinary 8-isoprostane and albumin excretion were observed in DOCA-salt compared with control mice (P < 0.05). Periodic acid-Schiff and Masson's trichrome staining showed more severe glomerulosclerosis and tubulointerstitial injury in the renal cortex in DOCA-salt compared with control mice, respectively (P < 0.05). Hydroxyproline assay and F4/80-staining showed that renal collagen levels and interstitial monocyte/macrophage infiltration were greater in DOCA-salt compared with control mice, respectively (P < 0.05). Blockade of the NK-1R with L-733,060 or RP-67580 in DOCA-salt mice suppressed increments in urinary 8-isoprostane and albumin excretion, interstitial monocyte/macrophage infiltration, and glomerulosclerosis and tubulointerstitial injury and fibrosis (P < 0.05). Thus, our data show that blockade of the NK-1Rs alleviates renal functional and tissue injury in the absence of alteration in blood pressure in DOCA-salt-hypertensive mice. The results suggest that elevated SP levels during DOCA-salt hypertension play a significant role contributing to renal damage possibly via enhancing oxidative stress and macrophage infiltration of the kidney.

UVA-induced calcium oscillations in rat mast cells

UVA is a major bio-active component in solar irradiation, and is shown to have immunomodulatory and anti-inflammatory effects. The detailed molecular mechanism of UVA action in regard to calcium signaling in mast cells, however, is not fully understood. In this study, it was found that UVA induced ROS formation and cytosolic calcium oscillations in individual rat mast cells. Exogenously added H2O2 and hypoxanthine/xanthine oxidase (HX/XOD) mimicked UVA effects on cytosolic calcium increases. Regular calcium oscillation induced by UVA irradiation was inhibited completely by the phosphatidylinositol-specific phospholipase C inhibitor U73122, but U73343 was without effect. Tetrandrine, a calcium entry blocker, or calcium-free buffer abolished UVA-induced calcium oscillations. L-type calcium channel blocker nifedipine and stores-operated calcium channel blocker SK&F96365 had no such inhibitory effect. ROS induction by UVA was abolished after pre-incubation with anti-oxidant NAC or with NAD(P)H oxidase inhibitor DPI; such treatment also made UVA-induced calcium oscillation to disappear. UVA irradiation did not increase mast cell diameter, but it made mast cell structure more granular. Spectral confocal imaging revealed that the emission spectrum of the endogenous fluorophore in single mast cell contained a sizable peak which corresponded to that of NAD(P)H. Taken together, these data suggest that UVA in rat mast cells could activate NAD(P)H oxidase, to produce ROS, which in turn activates phospholipase C signaling, to trigger regular cytosolic calcium oscillation.

Procyanidin C1 from apple extracts inhibits Fc epsilon RI-mediated mast cell activation

BACKGROUND

Polyphenol-enriched fractions, which are extracted from unripe apples (Rosaceae, Malus spp.), consisting of procyanidins (polymers of catechins) are known to have an anti-allergenic effect on patients with various allergic diseases. Although it has been reported that apple extracts inhibit histamine release from mast cells, the molecular mechanisms for this anti-allergenic effect are not well understood. To elucidate the molecular mechanisms by which apple extracts induce their anti-allergenic effects, the effects of purified apple extract components on high-affinity receptors for IgE (Fc epsilon RI)-mediated mast cell activation were investigated.

METHODS

The anti-allergic effect of oral administration of apple procyanidin extracts on passive cutaneous anaphylactic responses of BALB/c mice was assessed. We evaluated the effects of procyanidin C1 (PC1) [epicatechin-(4beta-->8)-epicatechin-(4beta-->8)-epicatechin], a component of the procyanidin fraction, on mouse bone-marrow-derived mast cell degranulation, cytokine production, protein tyrosine phosphorylation and on the generation of intracellular reactive oxygen species (ROS) of cells stimulated by Fc epsilon RI cross-linking in vitro.

RESULTS

In an in vivo study, oral administration of the procyanidin fraction suppressed the mast-cell-dependent allergic reaction. In in vitro studies, PC1 dose-dependently decreased Fc epsilon RI-mediated degranulation and cytokine production of mast cells. Furthermore, PC1 inhibited tyrosine phosphorylation of Syk and linker for activation of T cells, and the ROS generation in stimulated mast cells.

CONCLUSIONS

PC1 suppresses Fc epsilon RI-mediated mast cell activation by inhibiting intracellular signaling pathways. These observations provide evidence for the anti-allergenic effects of the procyanidin-enriched apple extract.

A neurokinin-1 receptor antagonist that reduces intra-abdominal adhesion formation decreases oxidative stress in the peritoneum

Oxidative stress has been implicated in intra-abdominal adhesion formation. Substance P, a neurokinin-1 receptor (NK-1R) ligand, facilitates leukocyte recruitment and reactive oxygen species (ROS) generation. We have shown in a rat model of adhesion formation that intraperitoneal administration of a NK-1R antagonist at the time of abdominal operation reduces postoperative adhesion formation. Thus we determined the effects of NK-1R antagonist administration on peritoneal leukocyte recruitment and oxidative stress within 24 h of surgery. Adhesions were induced in Wistar rats randomly assigned to receive the antagonist or vehicle intraperitoneally. Peritoneal tissue was isolated at 2, 4, 6, and 24 h after surgery for analysis of the oxidative stress biomarkers 8-isoprostane (8-IP), protein carbonyl, NADPH oxidase, myeloperoxidase (MPO), and ICAM-1 and VCAM-1 mRNAs. Total antioxidant capacity of peritoneal fluid was also determined. MPO, NADPH oxidase, 8-IP, and protein carbonyl were elevated (P < 0.05) by 6 h. ICAM-1 mRNA was elevated (P < 0.05) by 2 h, whereas VCAM-1 levels decreased (P < 0.05) at 24 h. The NK-1R antagonist delayed the MPO rise and reduced (P < 0.05) 8-IP levels by 6 h and ICAM-1 mRNA, VCAM-1 mRNA, and protein carbonyl at 2 h. The antagonist also increased (P < 0.05) the antioxidant capacity of peritoneal fluid at all time points. These data further support a role for oxidative stress in adhesion formation and suggest that the NK-1R antagonist may limit adhesions, in part, by reducing postoperative oxidative stress through an inhibition of neutrophil recruitment and an increase in peritoneal fluid antioxidant capacity.

Modulation of the inflammatory response to histamine by terbutaline and sodium nitroprusside in guinea-pig skin

We measured the microvascular response (vasodilatation and plasma exudation) to skin prick provocations with histamine, terbutaline, sodium nitroprusside (SNP) and the combinations of terbutaline and histamine as well as SNP and histamine in guinea-pig skin. The response was measured by external detection of beta radiation from transferrin labelled with (113m)In. Histamine induced a moderate microvascular response. Terbutaline alone induced a smaller response, probably reflecting vasodilatation. When added to histamine, terbutaline significantly reduced the microvascular response to histamine. The response to histamine, SNP and the combination of histamine and SNP were all similar. We conclude that the anti-inflammatory effect of terbutaline can be readily measured with this technique. We found no indication of a pro-inflammatory effect of SNP when combined with histamine. Rather, the lack of additive effect may suggest an anti-inflammatory effect of SNP on the response to histamine.

NK-1 antagonist CP99994 inhibits stress-induced mast cell degranulation in rats

Mast cells are implicated in stress-induced inflammatory skin diseases such as psoriasis. Mechanisms of stress-induced mast cell degranulation however, are not entirely clear. Here we explore the role of activation of a Substance P (SP) receptor (NK-1) on mast cell degranulation upon exposure to stress in rats. A specific nonpeptide NK-1 antagonist, CP99994 was used to treat the rats either peripherally or intracerebroventricularly. Because increased SP activity in the brain may mediate the stress response, we also examined cutaneous mast cell degranulation after central injection of SP. Stress, as well as SP injected centrally, increased mast cell degranulation. Both central and peripheral injection of CP99994 prevented stress-induced mast cell degranulation. Surprisingly, the combination of stress with SP decreased mast cell degranulation, suggesting that high levels of SP may counteract the stress responses. Results in this animal model suggest that NK-1 antagonists may be used therapeutically to treat stress-induced inflammatory skin diseases; however, drug doses should be chosen carefully.

Reactive oxygen species in sustained airway constriction induced by citric acid aerosol inhalation

We tested if there is a direct relationship between reactive oxygen species and citric acid-induced airway constriction. Guinea pigs were divided into two groups: control and dimethylthiourea (a hydroxyl radical scavenger). The animals in each group were further separated into four subgroups: baseline, recovery 2-3 min, recovery 10 min, and recovery 20 min. Each animal was anesthetized, cannulated, paralyzed, and artificially ventilated. Citric acid aerosol inhalation caused the following significant changes in the control group during the recovery period: airway constriction for at least 20 min, increases in luminol-amplified t-butyl hydroperoxide-initiated chemiluminescence counts in the bronchoalveolar lavage samples at 2-3 and 20 min, an increase in bronchoalveolar lavage fluid substance P level at 2-3 min, and elevations in the bronchoalveolar lavage fluid total cell and neutrophil numbers at 20 min. All citric acid-induced alterations were prevented by dimethylthiourea pretreatment. These results suggest that citric acid inhalation induces the initial release of reactive oxygen species and tachykinins, which causes further cellular infiltration and sustained airway constriction.

Reactive oxygen species generation and histamine release by activated mast cells: modulation by nitric oxide synthase inhibition

1. We have examined the generation of intracellular reactive oxygen species (ROS) and release of histamine by rat peritoneal mast cells (RPMC) in response to stimulation with antigen (ovalbumin), compound 48/80, nerve growth factor (NGF) and substance P (SP). 2. We have also examined the effects of the non-specific nitric oxide synthase inhibitor, L-NAME (100 microM) upon the release of histamine and generation of intracellular ROS in response to the named secretagogues. 3. Ovalbumin (100 - 1000 microg ml-1), compound 48/80 (0.1 - 100 microg ml-1), NGF (0.1 - 100 microg ml-1), and SP (5 - 50 microM), caused a concentration-dependent release of histamine from RPMC. 4. Ovalbumin (1 ng ml-1 - 0.1 microg ml-1), compound 48/80 (1 - 100 microg ml-1), NGF (1 pg ml-1 - 1 microg ml-1), and SP (0.005 - 50 microM) caused a concentration-dependent generation of intracellular ROS by RPMC. 5. Pre-incubation of RPMC with L-NAME (100 microM) caused a significant enhancement of both histamine release and intracellular ROS from RPMC in response to ovalbumin, compound 48/80, NGF and SP. 6. Our data demonstrate that NGF, SP and ovalbumin are capable of causing intracellular ROS generation by RPMC at lower concentrations than those causing significant histamine release and we speculate that this may contribute to the activation of cytokine production. 7. The data also show that NO modulates histamine release, and ROS generation in response to the secretagogues used. This may have significance in pathologies where NO synthesis is decreased, leading to an increased activation of mast cells.