Effect of Intervention in Mast Cell Function Before Reperfusion on Renal Ischemia-Reperfusion Injury in Rats.

BACKGROUND/AIMS: Mast cells are sparsely distributed in the kidneys under normal conditions; however, the number of mast cells increases dramatically during renal ischemia/reperfusion injury (RI/RI). When mast cells are stimulated, numerous mediators are released, and under pathological conditions, they produce a wide range of biological effects. The aim of this study was to investigate the effect of intervention in mast cell function before reperfusion on RI/RI. METHODS: Sprague-Dawley (SD) rats (n=50) were randomized into five groups: sham group, ischemia/reperfusion (I/R) group, cromolyn sodium treatment group (CS+I/R group), ketotifen treatment group (K+I/Rgroup), and compound 48/80 treatment group (C+I/R group). I/R injury was induced by bilateral renal artery and vein occlusion for 45 min followed by 24 h of reperfusion. The agents were intravenously administered 5 min before reperfusion through the tail vein. The serum levels of blood urea nitrogen(BUN), serum creatinine (Scr) and histamine and the kidney levels of malondialdehyde (MDA), superoxide dismutase (SOD), tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) were assessed. The expression of intracellular adhesion molecule-1 (ICAM-1) in renal tissue was also measured. RESULTS: I/R injury resulted in severe renal injury, as demonstrated by a large increase in injury scores; serum levels of BUN, Scr and histamine; and kidney levels of MDA, TNF-α, and IL-6; this was accompanied by reduced SOD activity and upregulated ICAM-1 expression. Treatment with cromolyn sodium or ketotifen markedly alleviated I/R-mediated kidney injury, whereas compound 48/80 further aggravated kidney injury. CONCLUSION: Intervention in mast cell activity prior to reperfusionhas a strong effect on RI/RI.

Cross-protection against influenza virus infection by intranasal administration of nucleoprotein-based vaccine with compound 48/80 adjuvant.

The nucleoprotein (NP) of influenza viruses is highly conserved and therefore has become one of the major targets of current universal influenza vaccine (UIV) studies. In this study, the recombinant nucleoprotein (NP) of the A/PR/8/34 (H1N1) influenza virus strain was expressed using an Escherichia coli (E. coli) expression system and then purified as a candidate UIV. The NP protein was administered intranasally or intraperitoneally twice at 3-week intervals to female BALB/c mice in combination with C48/80 adjuvant. Then, the mice were challenged with homologous or heterologous influenza viruses at a lethal dose 3 weeks after the last immunization. The results showed that the serum IgG titers of all of the mice immunized with NP reached a higher level and the protection provided by NP vaccine against the homologous virus depended on the administered dosage and adjuvant. In addition, immunization with 100 µg NP in combination with C48/80 adjuvant could provide good cross-protection against heterologous H9N2 avian influenza viruses. This study indicated that NP as a candidate antigen of UIV immunized intranasally could effectively induce mucosal and cell-mediated immunity, with the potential to control epidemics caused by the appearance of new emerging influenza viruses.

Theanine is a candidate amino acid for pharmacological stabilization of mast cells.

The increasing occurrences of allergic disorders may be attributed to exposure to environmental factors that contribute to the pathogenesis of allergy. The health benefits of green tea have been widely reported but are largely unsubstantiated. Theanine is the major amino acid present in green tea. In this study, we investigated the role of theanine in both IgE- and non- IgE-induced allergic response. Theanine inhibited compound 48/80-induced systemic anaphylactic shock and ear swelling responses. IgE-mediated passive cutaneous anaphylaxis was inhibited by the oral administration or pharmaceutical acupuncture of theanine. Histamine release from mast cells was decreased with the treatment of theanine. Theanine also repressed phorbol 12-myristate 13-acetate and calcium ionophore A23187-induced TNF-α, IL-1ß, IL-6, and IL-8 secretion by suppressing NF-κB activation. Furthermore, theanine suppressed the activation of caspase-1 and the expression of receptor interacting protein-2. The current study demonstrates for the first time that theanine might possess mast cell-stabilizing capabilities.

SCH23390, a dopamine D1 receptor antagonist, suppressed scratching behavior induced by compound 48/80 in mice.

To clarify the mechanisms by which compound 48/80 (C48/80) induces scratching behavior, the involvement of dopamine D(1) receptors was investigated. The intracisternal (i.t.) administration of SCH23390 (1.0 µg), a selective dopamine D(1) receptor antagonist, significantly decreased C48/80-induced scratching behavior in mice. These results suggest that dopamine D(1) receptors contribute to scratching behavior or the itch sensation induced by subcutaneous injection of C48/80 in mice. Co-administration of SCH23390 and C48/80 enhanced c-fos immunoreactivities in the peduncular part of the lateral hypothalamus (PLH), whereas the immunoreactivities in the other groups were unchanged. The dopaminergic system may be playing an important role in the suppression of C48/80-induced scratching behavior by SCH23390.

Mast cell activation in vivo impairs the macrophage reverse cholesterol transport pathway in the mouse.

OBJECTIVE: Chymase released by activated mast cells degrades high-density lipoproteins. We evaluated whether local activation of mast cells would attenuate cholesterol efflux from neighboring macrophage foam cells, thereby disrupting the entire in vivo pathway of macrophage-specific reverse cholesterol transport (RCT). METHODS AND RESULTS: C57Bl/6J mice received intraperitoneal injections of the mast cell-degranulating compound 48/80 to induce peritoneal mast cell activation, human apolipoprotein A-I (apoA-I) to stimulate RCT, and [(3)H]cholesterol-labeled J774 macrophages for measurement of the rate of RCT. After 3 hours, (3)H-radioactivity was measured in the intestinal lumen contents. Activation of mast cells in the peritoneal cavity depleted human apoA-I pre-ß-migrating species, impairing the ability of the peritoneal fluid to efficiently promote cholesterol efflux from cultured macrophages. Moreover, intact but not chymase-treated (proteolyzed) apoA-I accelerated the transfer of macrophage-derived (3)H- radioactivity to the intestinal contents. Importantly, stimulation of RCT by human apoA-I was fully blocked by 48/80 in mast cell-competent wild-type C57Bl/6J mice but not in mast cell-deficient W-sash c-kit mutant mice. The ability of intraperitoneally administered phospholipid vesicles to promote RCT in wild-type mice was not blocked by 48/80, supporting the notion that mast cell-dependent proteolysis of the intraperitoneally administered apoA-I was responsible for RCT inhibition. CONCLUSIONS: Overall, our results suggest that tissue-specific activation of mast cells with ensuing release of chymase is able to proteolytically inactivate apoA-I in the microenvironment of the activated mast cells, thus locally impairing the initiation of macrophage RCT in vivo.

Expression of type I GNRH receptor and in vivo and in vitro GNRH-I effects in corpora lutea of pseudopregnant rabbits.

The expression of type I GNRH receptor (GNRHR-I) and the direct role of GNRH-I on corpora lutea (CL) function were studied in the pseudopregnant rabbit model. Immunohistochemistry evidenced GNRHR-I and GNRH-I in luteal cells at early (day 4 pseudopregnancy)-, mid (day 9)-, and late (day 13)-luteal stages. Real-time RT-PCR and western blotting revealed GNRHR-I mRNA and protein at the three luteal stages. Buserelin in vivo treatment at days 9 and 13 decreased plasma progesterone levels for 48 and 24  h respectively. In in vitro cultured CL, buserelin reduced progesterone secretion, increased prostaglandin F(2α) (PGF(2α)) secretion and cyclo-oxygenase-2 (COX-2) and nitric oxide synthase (NOS) activities at days 9 and 13, and decreased PGE2 at day 13. Co-incubation with antagonists for GNRH-I (antide), inositol 1,4,5-trisphosphate (IP3, 2-amino-ethoxydiphenylborate), and diacylglycerol (DAG, 1-hexadecyl-2-acetyl glycerol) or inhibitors for phospholipase C (PLC, compound 48/80), and protein kinase C (PKC, staurosporine) counteracted the buserelin effects. Buserelin co-incubated with COX inhibitor (acetylsalicylic acid) increased progesterone and decreased PGF(2α) and NOS activity at days 9 and 13, whereas co-incubation with NOS inhibitor (N-nitro-l-arginine methyl ester) increased progesterone at the same luteal stages. These results suggest that GNRHR-I is constitutively expressed in rabbit CL independently of luteal stage, whereas GNRH-I down-regulates directly CL progesterone production via PGF(2α) at mid- and late-luteal stages of pseudopregnancy, utilizing its cognate type I receptor with a post-receptorial mechanism that involves PLC, IP3, DAG, PKC, COX-2, and NOS.

Artemisia iwayomogi inhibits immediate-type allergic reaction and inflammatory cytokine secretion.

The immediate-type allergic reaction is involved in many allergic diseases such as asthma and allergic rhinitis. The discovery of drugs for the treatment of immediate-type allergic diseases is a very important subject in human health. In this study, we investigated the effect of Artemisia iwayomogi (AIAE) on mast cell-mediated allergic reaction and inflammatory cytokine secretion. AIAE inhibited compound 48/80-induced systemic reactions in mice. AIAE decreased the passive cutaneous anaphylaxis (PCA) reaction activated by antidinitrophenyl (anti-DNP) IgE antibody. AIAE dose-dependently reduced histamine release from rat peritoneal mast cells activated by compound 48/80 or anti-DNP IgE. Furthermore, AIAE attenuated the phorbol 12-myristate 13-acetate plus calcium ionophore A23187-stimulated tumor necrosis factor-alpha and interleukin-6 secretion in human mast cells. These results provide evidence that AIAE may be beneficial in the treatment of allergic diseases.

Anti-allergic effects of Lycopus lucidus on mast cell-mediated allergy model.

The current study characterizes the mechanism by which the aqueous extract of Lycopus lucidus Turcz. (Labiatae) (LAE) decreases mast cell-mediated immediate-type allergic reaction. The immediate-type allergic reaction is involved in many allergic diseases such as asthma and allergic rhinitis. LAE has been used as a traditional medicine in Korea and is known to have an anti-inflammatory effect. However, its specific mechanism of action is still unknown. LAE was anally administered to mice for high and fast absorption. LAE inhibited compound 48/80-induced systemic reactions in mice. LAE decreased the local allergic reaction, passive cutaneous anaphylaxis, activated by anti-dinitrophenyl (DNP) IgE antibody. LAE dose-dependently reduced histamine release from rat peritoneal mast cells activated by compound 48/80 or anti-DNP IgE. Furthermore, LAE decreased the secretion of TNF-alpha and IL-6 in phorbol 12-myristate 13-acetate (PMA) plus calcium ionophore A23187-stimulated human mast cells. The inhibitory effect of LAE on the pro-inflammatory cytokine was p38 mitogen-activated protein kinase (MAPK) and nuclear factor-kappaB (NF-kappaB) dependent. LAE attenuated PMA plus A23187-induced degradation of IkappaBalpha and nuclear translocation of NF-kappaB, and specifically blocked activation of p38 MAPK, but not that of c-jun N-terminal kinase and extracellular signal-regulated kinase. Our findings provide evidence that LAE inhibits mast cell-derived immediate-type allergic reactions and involvement of pro-inflammatory cytokines, p38 MAPK, and NF-kappaB in these effects.

Anti-allergic effects of Artemisia iwayomogi on mast cell-mediated allergy model.

The discovery of drugs for the treatment of allergic disease is an important subject in human health. The Artemisia iwayomogi (Compositae) (AIE) has been used as a traditional medicine in Korea and is known to have an anti-inflammatory effect. However, its specific mechanism of action is still unknown. In this report, we investigated the effect of AIE on the mast cell-mediated allergy model and studied the possible mechanism of action. AIE inhibited compound 48/80-induced systemic reactions and plasma histamine release in mice. AIE decreased immunoglobulin E (IgE)-mediated local allergic reaction, passive cutaneous anaphylaxis (PCA) reaction. AIE dose dependently attenuated histamine release from rat peritoneal mast cells activated by compound 48/80 or IgE. AIE decreased the compound 48/80-induced intracellular Ca(2+). Furthermore, AIE decreased the phorbol 12-myristate 13-acetate (PMA) plus calcium ionophore A23187-stimulated tumor necrosis factor-alpha and interleukin-6 gene expression and production in human mast cells. The inhibitory effect of AIE on the proinflammatory cytokine was p38 mitogen-activated protein kinase (MAPK) and nuclear factor-kappaB (NF-kappaB) dependent. AIE attenuated PMA plus A23187-induced degradation of IkappaBalpha and nuclear translocation of NF-kappaB and specifically blocked activation of p38 MAPK but not that of c-jun N-terminal kinase and extracellular signal-regulated kinase. Our findings provide evidence that AIE inhibits mast cell-derived immediate-type allergic reactions and involvement of intracellular Ca(2+), proinflammatory cytokines, p38 MAPK, and NF-kappaB in these effects.

Isodon japonicus decreases immediate-type allergic reaction and tumor necrosis factor-alpha production.

BACKGROUND: The immediate-type allergic reaction is involved in many allergic diseases such as asthma, allergic rhinitis and sinusitis. The discovery of drugs for the treatment of immediate-type allergic disease is a very important subject in human health. Isodon japonicus Hara (Labiatae) (IJAE) has been used for centuries as a traditional medicine in Korea and is known to have an anti-inflammatory effect. However, its specific mechanism of action is still unknown. In this report, we investigated the effect of IJAE on the immediate-type allergic reaction and studied its possible mechanisms of action, focusing on the mast cell-mediated allergic reaction. METHODS: IJAE extracts were anally administered to mice for high and fast absorption. Compound 48/80-induced mortality and compound 48/80- or immunoglobulin E (IgE)-induced histamine release were measured to evaluate the antiallergic effects of IJAE. The effect of IJAE on the model of local allergic reaction in vivo, passive cutaneous anaphylaxis (PCA), was investigated. The production of tumor necrosis factor-alpha (TNF-alpha) was measured by Western blotting. RESULTS: IJAE inhibited compound 48/80-induced systemic reactions and plasma histamine release in mice. IJAE decreased the PCA reaction activated by anti-dinitrophenyl (DNP) IgE antibody. IJAE dose-dependently reduced histamine release from rat peritoneal mast cells activated by compound 48/80 or anti-DNP IgE. Furthermore, IJAE decreased the production of TNF-alpha in phorbol 12-myristate 13-acetate plus calcium ionophore A23187-stimulated human mast cells. CONCLUSION: Our findings provide evidence that IJAE inhibits mast cell-derived immediate-type allergic reactions, and also demonstrate the involvement of TNF-alpha in these effects. We propose the clinical use of IJAE in mast cell-mediated immediate-type allergic diseases.

Inhibitory effects of Xanthii fructus extract on mast cell-mediated allergic reaction in murine model.

The effect of aqueous extract of Xanthii fructus (XF) on mast cell-mediated allergic reaction has been investigated. XF inhibited compound 48/80-induced systemic anaphylaxis in mouse. This dose-dependently inhibited histamine release from rat peritoneal mast cells (RPMC) by compound 48/80. Additionally, XF inhibited local immunoglobulin E (IgE)-mediated passive cutaneous anaphylatic reaction. When XF (0.1mg/ml) was added, the secretion of tumor necrosis factor-alpha (TNF-alpha) from anti-dinitrophenyl (DNP) IgE antibody-stimulated mast cells was inhibited by 56%. Our studies provide evidence that XF may be beneficial in the treatment of various types allergic diseases.

Inhibitory effects of mast cell-mediated allergic reactions by cell cultured Siberian Ginseng.

The crude drug "Siberian Ginseng (SG)" has long been used in empirical Oriental medicine for the nonspecific enhancement of resistance in humans and animals. In this study, we investigated the effect of cell cultured SG by oral administration in mast cell-mediated allergic reactions. SG dose-dependently inhibited compound 48/80-induced systemic allergy with doses of 10(-2) to 1 g/kg 1 h before oral administration. Of special note, SG inhibited systemic allergy with the dose of 1 g/kg by 25%. SG (1 g/kg) also inhibited passive cutaneous allergic reaction by 51%. SG dose-dependently inhibited histamine release from rat peritoneal mast cells. When SG (0.01 mg/ml) was added, the secretion of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 in antidinitrophenyl (DNP) IgE antibody-stimulated mast cells was inhibited 39.5% and 23.3%, respectively. In addition, SG inhibited anti-DNP IgE antibody-stimulated TNF-alpha protein expression in mast cells. Our studies provide evidence that SG may be beneficial in the treatment of various types of allergic diseases.

Oral administration of a nitric oxide synthase inhibitor enhances de novo mammalian angiogenesis mediated by TNF-alpha, saline and mast-cell secretion.

In healthy adult rats, the test tissue that is used in the mesenteric-window angiogenesis assay is natively vascularized, lacks physiological angiogenesis, and is unperturbed by surgical intervention. Using the rat MWAA oral treatment with the nitric oxide (NO) synthase inhibitor Nw-nitro-L-arginine methyl ester (L-NAME) enhanced the angiogenic response (compared with controls receiving the inactive enantiomer D-NAME) following i.p. injections of (i) TNF-alpha at an approximate physiological dose, (ii) Compound 48/80, which is a highly selective secretagogue causing mast-cell secretion in situ and a very strong angiogenic response, and (iii) saline of a grade not made for infusion, causing a weak angiogenic response. Angiogenesis was assessed quantitatively using microscopic morphometry and image analysis in terms of objective variables recording the microvascular spatial extension, microvascular density, number and length of microvessel segments (extending between two successive branching points) and the degree of microvessel tortuosity. The data strongly suggest that endogenous NO inhibits all three mammalian angiogenesis reactions, although to a markedly different extent. Notably, the present data are virtually the opposite of those that have been reported from other mammalian angiogenesis models, the test tissues of which display deranged homeostasis, such as surgical intervention and/or ischemia.

The ex vivo effect of the herbal medicine sho-saiko-to on histamine release from rat mast cells.

A traditional Japanese herbal medicine, Shosaiko-to (SST), has been used orally to treat several chronic diseases. Since these have included allergic rhinitis and bronchial asthma, we investigated the effect of SST on histamine release and the intracellular Ca2+ response in mast cells ex vivo. A single dose of 1.0 g/kg SST was administered orally to immunized rats 2-12 h before death. Mast cells were then separated from peritoneal lavages and stimulated with antigen. SST at 3 h after oral administration most significantly inhibited histamine release. This inhibitory effect was dose-dependent and was weaker than that of tranilast. In contrast, SST at 3 h had no effect on the antigen-induced Ca2+ response of the mast cells and failed to inhibit compound 48/80-induced histamine release. Our findings show that SST indeed has an active anti-allergic effect. We suggest that SST inhibits IgE receptor-associated protein phosphorylation in the histamine release pathway.

Effect of the aqueous extract of Aquilaria agallocha stems on the immediate hypersensitivity reactions.

We investigated the effects of the aqueous extract of Aquilaria agallocha Roxb. (Thymelaeaceae) on the immediate hypersensitivity reactions. The aqueous extract of Aquilaria agallocha stems showed inhibitory effects on passive cutaneous anaphylaxis, anaphylaxis induced by compound 48/80, and histamine release from rat peritoneal mast cells (RPMC). The morphological examination also clearly showed that the extract prevented the degranulation of RPMC in rats. The level of compound 48/80-induced intracellular cAMP in RPMC, when the extract was added, significantly increased about 8-fold at 10 s compared with that of basal cells. These results suggest that the aqueous extract of Aquilaria agallocha stems inhibits the immediate hypersensitivity reaction by inhibition of histamine release from mast cells.

In vivo drug-response measurements in target tissues by microdialysis.

To study the suitability of the microdialysis technique for the measurement of target tissue pharmacodynamics in humans, the model compounds theophylline, milrinone, and compound 48/80 were administered locally by means of reversed microdialysis to the interstitial space of skeletal muscle or skin in 24 healthy volunteers. Simultaneously, interstitial concentrations of cyclic adenosine monophosphate (cAMP; as an indicator of phosphodiesterase activity) were measured in skeletal muscle, and interstitial concentrations of histamine (as an indicator of mast cell release) were measured in skin. In muscle, reversed microdialysis with milrinone led to a dose-dependent increase in interstitial cAMP concentrations (n = 8), whereas no significant effect on cAMP was observed for theophylline versus placebo (1.63 +/- 0.53 nmol/L; n = 6), even at local concentrations exceeding those attained after therapeutic doses. In skin, reversed microdialysis with compound 48/80 increased interstitial histamine concentration dose dependently versus placebo (5.99 +/- 2.74 nmol/L; n = 10). From our experiments in human skeletal muscle and skin, we concluded that microdialysis was a suitable technique for the characterization of in vivo drug response at the relevant target site. Extension of these measurements to several other human tissues is readily feasible.

Inhibition by actinomycin D of neurogenic mouse ear oedema.

We have investigated the effects of actinomycin D on mouse ear oedema induced by capsaicin, neuropeptides, and established inflammatory mediators. Actinomycin D (0.5 mg/kg, i.v.) significantly (P < 0.01) inhibited ear oedema induced by topical application of capsaicin, while adriamycin (6.0 mg/kg, i.v.) and cycloheximide (6.0 mg/kg, i.v.) had no effect on oedema. The ear oedema induced by intradermal injection of neuropeptides such as mammalian tachykinins, calcitonin gene-related peptide (CGRP), and vasoactive intestinal peptide (VIP), was markedly (P < 0.05, P < 0.01 or P < 0.001) suppressed by actinomycin D. The drug was also effective (P < 0.01 or P < 0.001) in inhibiting bradykinin (BK)- and compound 48/80-induced ear oedema, but did not inhibit oedema induced by histamine, 5-HT, leukotriene C4 (LTC4), and platelet activating factor (PAF) at a dose of 1 mg/kg. In mast cell-deficient W/WV mice, actinomycin D (1.0 mg/kg, i.v.) failed to inhibit substance P (SP)-induced ear oedema whereas spantide (0.5 mg/kg, i.v.) was an effective (P < 0.01) inhibitor of oedema formation. Furthermore, actinomycin D (10-100 microM) dose-dependently prevented histamine release from rat peritoneal mast cells evoked by SP, compound 48/80, and the ionophore A23182, respectively. These results strongly suggest that an inhibitory effect of actinomycin D on neurogenic inflammation is due primarily to the prevention of mast cell activation mediated by neuropeptides, rather than an interaction with DNA or receptors of neuropeptides.

Inhibition of carrageenin-induced rat paw oedema by crotapotin, a polypeptide complexed with phospholipase A2.

1. The effect of purified crotapotin, a non-toxic non-enzymatic chaperon protein normally complexed to a phospholipase A2 (PLA2) in South America rattlesnake venom, was studied in the acute inflammatory response induced by carrageenin (1 mg/paw), compound 48/80 (3 micrograms/paw) and 5-hydroxytryptamine (5-HT) (3 micrograms/paw) in the rat hind-paw. The effects of crotapotin on platelet aggregation, mast cell degranulation and eicosanoid release from guinea-pig isolated lung were also investigated. 2. Subplantar co-injection of crotapotin (1 and 10 micrograms/paw) with carrageenin or injection of crotapotin (10 micrograms/paw) into the contralateral paw significantly inhibited the carrageenin-induced oedema. This inhibition was also observed when crotapotin (10-30 micrograms/paw) was administered either intraperitoneally or orally. Subplantar injection of heated crotapotin (15 min at 60 degrees C) failed to inhibit carrageenin-induced oedema. Subplantar injection of crotapotin (10 micrograms/paw) also significantly inhibited the rat paw oedema induced by compound 48/80, but it did not affect 5-HT-induced oedema. 3. In adrenalectomized animals, subplantar injection of crotapotin markedly inhibited the oedema induced by carrageenin. The inhibitory effect of crotapotin was also observed in rats depleted of histamine and 5-HT stores. 4. Crotapotin (30 micrograms/paw) had no effect on either the histamine release induced by compound 48/80 in vitro or on the platelet aggregation induced by both arachidonic acid (1 nM) and platelet activating factor (1 microM) in human platelet-rich plasma. The platelet aggregation and thromboxane B2 (TXB2) release induced by thrombin (100 mu ml-1) in washed human platelets were also not affected by crotapotin. In addition, crotapotin (10 microg/paw) did not affect the release of 6-oxo-prostaglandin Fla, and TXB2 induced by ovalbumin in sensitized guinea-pig isolated lungs.5. Our results indicate that the anti-inflammatory activity of crotapotin is not due to endogenous corticosteroid release or inhibition of cyclo-oxygenase activity. It is possible that crotapotin may interact with extracellular PLA2 generated during the inflammatory process thereby reducing its hydrolytic activity.

Pericyte involvement in capillary sprouting during angiogenesis in situ.

To investigate the participation of microvascular pericytes in the process of capillary sprouting, we examined whole-mount preparations of the rat mesentery by use of a double immunofluorescence approach. Angiogenesis was induced by intraperitoneal injections of either the mast cell-degranulating substance compound 48/80 or tumor cell-conditioned medium. Capillary sprouts were visualized by staining with rhodamine-conjugated phalloidin and pericytes were simultaneously stained by an antibody to the intermediate filament protein desmin. Developing pericytes were negative for the smooth-muscle isoform of alpha-actin, but were clearly reactive for desmin. Pericytes appear to be involved in the earliest stages of capillary sprouting. Pericytes were regularly found lying at and in front of the advancing tips of endothelial sprouts. At many sites pericytes were seen to bridge the gap between the leading edges of opposing endothelial sprouts, which were apparently preparing to merge, suggesting that pericytic processes may serve as guiding structures aiding outgrowth of endothelial cells.

Evidence for the participation of mast cells in the innate resistance of mice to Schistosoma mansoni: effects on in vivo treatment with the ionophore 48-80

1. Evidence is presented for the participation of mast cells in the resistance of mice to infection by Schistosoma mansoni. 2. Intravenous injection of 1 microng/g body of the ionophore 48-80, a potent mast cell degranulator, significantly reduced (42-62%) the histamine content of the ear tisse of normal mice and either inceased or decreased resistance to parasite penetration and infection depending on whether the injection of the ionophore was i min or 2 days before cervarial penetration. 3. When 48-80 was injected 5 min before the benning of cercarial penetration, the number of parasites recovered from ear tissue 2 days later or from the portal system 30 days later was significantly reduced (39-71% and 27-40%, respectively) in relation to untreated controls. This resistance caused by 48-80 was blocked when mice were simultaneously treated with cyproheptadine, an antagonist of vasoactive amines. 4. In contrast, when 48-80 was administered 2 days before the beginning of cercarial penetration, the number of parasites retrieved from ear tissue 2 days later or from the portal system 30 days later was 32-64% and 28-30% larger, respectively, in relation to untreated controls. 5. These findings indicate that the local inflammatory reaction mediated by mast cells is important in the resistance of mice to infection with S. mansoni