Role of Pannexin-1-P2X7R signaling on cell death and pro-inflammatory mediator expression induced by Clostridioides difficile toxins in enteric glia.

Clostridioides difficile (C. difficile) produces toxins A (TcdA) and B (TcdB), both associated with intestinal damage and diarrhea. Pannexin-1 (Panx1) channels allows the passage of messenger molecules, such as adenosine triphosphate (ATP), which in turn activate the P2X7 receptors (P2X7R) that regulate inflammation and cell death in inflammatory bowel diseases. The aim of this study was to verify the effect of C. difficile infection (CDI) in the expression of Panx1 and P2X7R in intestinal tissues of mice, as well as their role in cell death and IL-6 expression induced by TcdA and TcdB in enteric glial cells (EGCs). Male C57BL/6 mice (8 weeks of age) were infected with C. difficile VPI10463, and the control group received only vehicle per gavage. After three days post-infection (p.i.), cecum and colon samples were collected to evaluate the expression of Panx1 by immunohistochemistry. In vitro, EGCs (PK060399egfr) were challenged with TcdA or TcdB, in the presence or absence of the Panx1 inhibitor (10Panx trifluoroacetate) or P2X7R antagonist (A438079), and Panx1 and P2X7R expression, caspase-3/7 activity and phosphatidylserine binding to annexin-V, as well as IL-6 expression were assessed. CDI increased the levels of Panx1 in cecum and colon of mice compared to the control group. Panx1 inhibitor decreased caspase-3/7 activity and phosphatidylserine-annexin-V binding, but not IL-6 gene expression in TcdA and TcdB-challenged EGCs. P2X7 receptor antagonist accentually reduced caspase-3/7 activity, phosphatidylserine-annexin-V binding, and IL-6 gene expression in TcdA and TcdB-challenged EGCs. In conclusion, Panx1 is increased during CDI and plays an important role in the effects of C. difficile toxins in EGCs, participating in cell death induced by both toxins by promoting caspase-3/7 activation via P2X7R, which is also involved in IL-6 expression induced by both toxins.

Host and Clostridioides difficile-Response Modulated by Micronutrients and Glutamine: An Overview.

Changes in intestinal microbiota are integral to development of Clostridioides difficile (C. difficile)-associated nosocomial diarrhea. Certain diets, especially Western diets, increase susceptibility to C. difficile infection (CDI). Here, we discuss recent findings regarding how nutrients modulate response of the host and C. difficile during infection. Calcium has a role in the sporulation and germination process. Selenium is effective in reducing the total amount of C. difficile toxin A (TcdA) and toxin B (TcdB) and in decreasing its cytotoxicity. In addition, selenium phosphate synthetase deficiency reduces C. difficile growth and spore production. On the other hand, iron has a dual role in C. difficile growth. For instance, high intracellular levels can generate reactive hydroxyl radicals, whereas low levels can reduce its growth. In humans, zinc deficiency appears to be related to the recurrence of CDI, in contrast, in the CDI model in mice a diet rich in zinc increased the toxin's activity. Low vitamin D levels contribute to C. difficile colonization, toxin production, and inflammation. Furthermore, glutamine appears to protect intestinal epithelial cells from the deleterious effects of TcdA and TcdB. In conclusion, nutrients play an important role in modulating host and pathogen response. However, further studies are needed to better understand the mechanisms and address some controversies.

Successful Pre-Clinical Management of Irinotecan-Debilitated Animals: A Protein- Based Accessory Phytomedicine.

BACKGROUND: Calotropis procera is a laticiferous plant (Apocynaceae) found in tropical regions all over the world. The ultrastructural characteristics of laticifers, their restricted distribution among different taxonomic groups, and in some species in each clade, as peptidases from latex, make them very attractive for biological analysis. OBJECTIVE: The study aims to investigate the effects of LP-PII-IAA (laticifer protein (LP) sub-fraction II (PII) of C. procera presenting an iodoacetamide-inhibited cysteine proteinase activity) on irinotecan-induced intestinal mucositis, a serious adverse effect of this medicine for the treatment of cancer. METHODS: LP-PII-IAA is composed of closely related isoforms (90%) of peptidases derived from catalysis and an osmotin protein (5%). Animals receiving co-administration of LP-PII-IAA presented a significant decrease in mortality, absence of diarrhea, histological preservation, and normalization of intestinal functions. RESULTS: Clinical homeostasis was accompanied by a reduction in MPO activity and declined levels of IL-1ß, IL-6 and KC, while the IL-10 level increased in LP-PII-IAA-treated animals. COX-2 and NF-kB immunostaining was reduced and the levels of oxidative markers (GSH, MDA) were normalized in animals that received LP-PII-IAA. CONCLUSION: We suggest that peptidases from the latex of Calotropis procera were instrumental in the suppression of the adverse clinical and physiological effects of irinotecan.

Increased Oxidative Stress in Gastric Cancer Patients and Their First-Degree Relatives: A Prospective Study from Northeastern Brazil.

BACKGROUND AND AIMS: First-degree relatives of gastric cancer patients are at increased risk of developing gastric cancer. Increased oxidative stress, including lipid peroxidation, has been associated with gastric carcinogenesis. Whether first-degree relatives of gastric cancer patients have increased oxidative stress remains unknown. We aimed to compare oxidative stress in patients with gastric cancer, their first-degree relatives, and dyspeptic controls. METHODS: A total of 155 patients undergoing upper endoscopy were prospectively enrolled, including 50 with gastric cancer, 49 first-degree relatives of gastric cancer patients, and 56 controls. Serum concentrations of malondialdehyde (MDA) and glutathione) and activities of superoxide dismutase (SOD) and catalase were measured. Multivariate analysis adjusting for sex, age, smoking status, and alcohol consumption was performed. RESULTS: Lipid peroxidation, as measured by concentration of MDA (nmol/mL), was higher (p = 0.04), and glutathione levels were lower (p < 0.001) in the gastric cancer group compared to controls. There was no difference in the catalase activity among the groups. There was no difference in glutathione and MDA concentration or catalase activity between the different stages of gastric cancer based on the TNM classification. Relatives of gastric cancer patients had higher glutathione concentration (µmol/mL) compared to gastric cancer patients (262.5 vs. 144.6; p = 0.018), while there was no difference in MDA concentration. Catalase and superoxide dismutase activity were lower in the gastric cancer group (3.82 vs. 0.91; p < 0.001 and 1.04 vs. 0.6; p < 0.001) compared to their first-degree relatives. Interestingly, MDA concentration in the first-degree relative group was higher than in the control group (7.9 vs. 5.1; p = 0.03). CONCLUSIONS: In this study, similarly to gastric cancer patients, their first-degree relatives were found to have increased oxidative stress compared to controls. Further studies are warranted to validate this observation and to better understand the role of oxidative stress as a possible biomarker in this population.

Clostridioides difficile Toxin A-Induced Wnt/ß-Catenin Pathway Inhibition Is Mediated by Rac1 Glucosylation.

Clostridioides difficile toxin A (TcdA) has been shown to inhibit cellular Wnt signaling, the major driving force behind the proliferation of epithelial cells in colonic crypts, likely through the inhibition of ß-catenin nuclear translocation. Herein, we aimed to advance the understanding of this mechanism by replicating the findings in vivo and by investigating the specific role of Rac1, a member of the Rho GTPase family, on the inhibition of the Wnt-induced ß-catenin nuclear translocation triggered by TcdA. To investigate the effects of TcdA on the Wnt/ß-catenin pathway in vivo, we injected the ileal loops of C57BL/6 mice with TcdA [phosphate-buffered saline (PBS) as the control] to induce C. difficile disease-like ileitis. After 4 h post-injection, we obtained ileum tissue samples to assess Wnt signaling activation and cell proliferation through Western blotting, immunohistochemistry, and qPCR. To assess the role of Rac1 on Wnt signaling inhibition by TcdA, we transfected rat intestinal epithelial cells (IEC-6) with either a constitutively active Rac1 plasmid (pcDNA3-EGFP-Rac1-Q61L) or an empty vector, which served as the control. We incubated these cells with Wnt3a-conditioned medium (Wnt3a-CM) to induce Wnt/ß-catenin pathway activation, and then challenged the cells with TcdA. We assessed Wnt signaling activation in vitro with TOP/FOPflash luciferase assays, determined nuclear ß-catenin translocation by immunofluorescence, measured cyclin D1 protein expression by Western blotting, and quantified cell proliferation by Ki67 immunostaining. In vivo, TcdA decreased ß-catenin, cyclin D1, and cMYC expression and inhibited the translocation of ß-catenin into the nucleus in the ileum epithelial cells. In addition, TcdA suppressed cell proliferation and increased Wnt3a expression, but did not alter Rac1 gene expression in the ileum tissue. In vitro, constitutively active Rac1 prevented Wnt signaling inhibition by enabling the ß-catenin nuclear translocation that had been blocked by TcdA. Our results show that TcdA inhibits Wnt/ß-catenin pathway in vivo and demonstrate that this inhibition is likely caused by a Rac1-mediated mechanism.

Anti-inflammatory latex proteins of the medicinal plant Calotropis procera: a promising alternative for oral mucositis treatment.

OBJECTIVE AND DESIGN: Oral mucositis (OM) is an intense inflammatory reaction progressing to tissue damage and ulceration. The medicinal uses of Calotropis procera are supported by anti-inflammatory capacity. PII-IAA, a highly homogenous cocktail of laticifer proteins (LP) prepared from the latex of C. procera, with recognized pharmacological properties was tested to treat OM. MATERIALS AND SUBJECTS: Male Golden Sirius hamsters were used in all treatments. TREATMENT: The latex protein samples were injected i.p. (5 mg/Kg) 24 h before mucositis induction (mechanical trauma) and 24 h later. METHODS: Histology, cytokine measurements [ELISA], and macroscopic evaluation [scores] were performed. RESULTS: PII-IAA eliminated OM, accompanied by total disappearance of myeloperoxidase activity and release of IL-1b, as well as reduced TNF-a. Oxidative stress was relieved by PII-IAA treatment, as revealed by MDA and GSH measurements. PII-IAA also reduced the expression of adhesion molecules (ICAM-1) and Iba-1, two important markers of inflammation, indicating modulatory effects. Histological analyses of the cheek epithelium revealed greater deposition of type I collagen fibers in animals given PII-IAA compared with the control group. This performance was only reached when LPPII was treated with iodoacetamide (IAA), an irreversible inhibitor of proteolytic activity of cysteine proteases. The endogenous proteolytic activity of LPPII induced adverse effects in animals. Candidate proteins involved in the phytomodulatory activity are proposed. CONCLUSIONS: Therapy was successful in treating OM with the laticifer protein fraction, containing peptidases and osmotin, from Calotropis procera. The effective candidate from the latex proteins for therapeutic use is PII-IAA.

5-Fluorouracil Induces Enteric Neuron Death and Glial Activation During Intestinal Mucositis via a S100B-RAGE-NFκB-Dependent Pathway.

5-Fluorouracil (5-FU) is an anticancer agent whose main side effects include intestinal mucositis associated with intestinal motility alterations maybe due to an effect on the enteric nervous system (ENS), but the underlying mechanism remains unclear. In this report, we used an animal model to investigate the participation of the S100B/RAGE/NFκB pathway in intestinal mucositis and enteric neurotoxicity caused by 5-FU (450 mg/kg, IP, single dose). 5-FU induced intestinal damage observed by shortened villi, loss of crypt architecture and intense inflammatory cell infiltrate as well as increased GFAP and S100B co-expression and decreased HuC/D protein expression in the small intestine. Furthermore, 5-FU increased RAGE and NFκB NLS immunostaining in enteric neurons, associated with a significant increase in the nitrite/nitrate, IL-6 and TNF-α levels, iNOS expression and MDA accumulation in the small intestine. We provide evidence that 5-FU induces reactive gliosis and reduction of enteric neurons in a S100B/RAGE/NFκB-dependent manner, since pentamidine, a S100B inhibitor, prevented 5-FU-induced neuronal loss, enteric glia activation, intestinal inflammation, oxidative stress and histological injury.

Nanoparticles targeting extra domain B of fibronectin-specific to the atherosclerotic lesion types III, IV, and V-enhance plaque detection and cargo delivery.

Extra domain B of fibronectin (FN-EDB) is upregulated in the extracellular matrix during tissue remodeling and has been postulated as a potential biomarker for atherosclerosis, yet no systematic test for FN-EDB in plaques has been reported. We hypothesized that FN-EDB expression would intensify in advanced plaques. Furthermore, engineering of FN-EDB-targeted nanoparticles (NPs) could enable imaging/diagnosis and local delivery of payloads to plaques. Methods: The amount of FN-EDB in human atherosclerotic and normal arteries (ages: 40 to 85 years) was assessed by histological staining and quantification using an FN-EDB-specific aptide (APTFN-EDB). FN-EDB-specific NPs that could serve as MRI beacons were constructed by immobilizing APTFN-EDB on the NP surface containing DTPA[Gd]. MRI visualized APTFN-EDB-[Gd]NPs administered to atherosclerotic apolipoprotein E-deficient mice in the brachiocephalic arteries. Analysis of the ascending-to-descending thoracic aortas and the aortic roots of the mice permitted quantitation of Gd, FN-EDB, and APTFN-EDB-[Gd]NPs. Cyanine, a model small molecule drug, was used to study the biodistribution and pharmacokinetics of APTFN-EDB-NPs to evaluate their utility for drug delivery. Results: Atherosclerotic tissues had significantly greater FN-EDB-positive areas than normal arteries (P < 0.001). This signal pertained particularly to Type III (P < 0.01), IV (P < 0.01), and V lesions (P < 0.001) rather than Type I and II lesions (AHA classification). FN-EDB expression was positively correlated with macrophage accumulation and neoangiogenesis. Quantitative analysis of T1-weighted images of atherosclerotic mice revealed substantial APTFN-EDB-[Gd]NPs accumulation in plaques compared to control NPs, conventional MRI contrast agent (Gd-DTPA) or accumulation in wild-type C57BL/6J mice. Additionally, the APTFN-EDB-NPs significantly prolonged the blood-circulation time (t1/2: ~ 6 h) of a model drug and increased its accumulation in plaques (6.9-fold higher accumulation vs. free drug). Conclusions: Our findings demonstrate augmented FN-EDB expression in Type III, IV, and V atheromata and that APTFN-EDB-NPs could serve as a platform for identifying and/or delivering agents locally to a subset of atherosclerotic plaques.

5-Fluorouracil induces inflammation and oxidative stress in the major salivary glands affecting salivary flow and saliva composition.

This study aimed to elucidate the effect of 5-fluorouracil (5-FU) on the histological aspects of the major salivary glands, salivary flow and saliva composition using an established oral mucositis model in hamsters. Oral mucositis was induced by two intraperitoneal administrations of 5-FU in two consecutive days (60 and 40mg/kg), followed by cheek pouch mucosa scratch, on day 4. The Pilocarpine-stimulated salivary flow was measured 4 and 10days after the first 5-FU injection. Salivary glands were harvested for histopathological analysis, measurement of inflammatory cells, quantification of pro-inflammatory cytokines (TNF-α and IL-1ß), investigation of cell death and cell proliferation. Oxidative stress and oxidative defense system were also investigated in the salivary gland tissues using MDA (malondialdehyde), nitrite, non-protein sulfhydryl groups (NP-SH), SOD (superoxide dismutase) and CAT (catalase). In addition, the CAT and lysozyme activities and the IgA and SOD levels were evaluated in the saliva samples. 5-FU significantly reduced the pilocarpine-stimulated salivary flow rate on the 4th experimental day, associated with an increase in the SOD levels in saliva. Recovery of the salivary flow and SOD were observed on day 10, when an increase in the saliva lysozyme levels was detected. In addition, 5-FU promoted vacuolization in parotid (P) and periductal edema in submandibular (SM) gland, combined with an increase in the inflammatory cells influx, mostly observed on the 4th day in SM gland and on 4th and 10th days in P. Oxidative stress was found mostly on day 10 in SM, SL and P glands, associated with release of proinflammatory cytokines, observed in SM and SL glands, but not in P. 5-FU induces an inflammatory response in the major salivary glands, most observed ten days after its first injection, which may contribute to the major salivary glands hypofunction, leading to alterations in the salivary flow rate and composition.

Transforming Growth Factor ß1/SMAD Signaling Pathway Activation Protects the Intestinal Epithelium from Clostridium difficile Toxin A-Induced Damage.

Clostridium difficile, the main cause of diarrhea in hospitalized patients, produces toxins A (TcdA) and B (TcdB), which affect intestinal epithelial cell survival, proliferation, and migration and induce an intense inflammatory response. Transforming growth factor ß (TGF-ß) is a pleiotropic cytokine affecting enterocyte and immune/inflammatory responses. However, it has been shown that exposure of intestinal epithelium to a low concentration of TcdA induces the release of TGF-ß1, which has a protective effect on epithelial resistance and a TcdA/TGF-ß signaling pathway interaction. The activation of this pathway in vivo has not been elucidated. The aim of this study was to investigate the role of the TGF-ß1 pathway in TcdA-induced damage in a rat intestinal epithelial cell line (IEC-6) and in a mouse model of an ileal loop. TcdA increased the expression of TGF-ß1 and its receptor, TßRII, in vitro and in vivo TcdA induced nuclear translocation of the transcription factors SMAD2/3, a hallmark of TGF-ß1 pathway activation, both in IEC cells and in mouse ileal tissue. The addition of recombinant TGF-ß1 (rTGF-ß) prevented TcdA-induced apoptosis/necrosis and restored proliferation and repair activity in IEC-6 cells in the presence of TcdA. Together, these data show that TcdA induces TGF-ß1 signaling pathway activation and suggest that this pathway might play a protective role against the effect of C. difficile-toxin.

The involvement of mast cells in the irinotecan-induced enteric neurons loss and reactive gliosis.

BACKGROUND: The irinotecan (CPT-11) causes intestinal mucositis and diarrhea that may be related to changes in the enteric nervous system (ENS). In inflammatory condition, mast cells release a variety of pro-inflammatory mediators that can interact with the ENS cells. It has not been explored whether CPT-11 is able to alter the enteric glial and neuronal cell, and the role of mast cells in this effect. Therefore, this study was conducted to investigate the effect of CPT-11 on the enteric glial and neuronal cells, as well as to study the role of mast cells in the CPT-11-induced intestinal mucositis. METHODS: Intestinal mucositis was induced in Swiss mice by the injection of CPT-11 (60 mg/kg, i.p.) once a day for 4 days following by euthanasia on the fifth day. To investigate the role of mast cells, the mice were pretreated with compound 48/80 for 4 days (first day, 0.6 mg/kg; second day, 1.0 mg/kg; third day, 1.2 mg/kg; fourth day, 2.4 mg/kg) to induce mast cell degranulation before the CPT-11 treatment. RESULTS: Here, we show that CPT-11 increased glial fibrillary acidic protein (GFAP) and S100ß gene and S100ß protein expressions and decreased HuC/D protein expression in the small intestine segments. Concomitantly, CPT-11 enhanced tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels and inducible nitric oxide synthase (iNOS) gene expression, associated with an increase in the total number macrophages (positive cells for ionized calcium-binding adapter molecule, Iba-1) and degranulated mast cells in the small intestine segments and caused significant weight loss. The pretreatment with compound 48/80, an inductor of mast cells degranulation, significantly prevented these CPT-11-induced effects. CONCLUSIONS: Our data suggests the participation of mast cells on the CPT-11-induced intestinal mucositis, macrophages activation, enteric reactive gliosis, and neuron loss.

Correction: Topical HPMC/S-Nitrosoglutathione Solution Decreases Inflammation and Bone Resorption in Experimental Periodontal Disease in Rats.

[This corrects the article DOI: 10.1371/journal.pone.0153716.].

Topical HPMC/S-Nitrosoglutathione Solution Decreases Inflammation and Bone Resorption in Experimental Periodontal Disease in Rats.

S-nitrosoglutathione (GSNO) is a nitric oxide (NO) donor, which exerts antioxidant, anti-inflammatory, and microbicidal actions. Intragingival application of GSNO was already shown to decrease alveolar bone loss, inflammation and oxidative stress in an experimental periodontal disease (EPD) model. In the present study, we evaluated the potential therapeutic effect of topical applications of hydroxypropylmethylcellulose (HPMC)/GSNO solutions on EPD in Wistar rats. EPD was induced by placing a sterilized nylon (3.0) thread ligature around the cervix of the second left upper molar of the animals, which received topical applications of a HPMC solutions containing GSNO 2 or 10 mM or vehicle (HPMC solution), 1 h prior to the placement of the ligature and then twice daily until sacrifice on day 11. Treatment with HPMC/GSNO 10 mM solution significantly reduced alveolar bone loss, oxidative stress and TNF-α e IL-1ß levels in the surrounding gingival tissue, and led to a decreased transcription of RANK and TNF-α genes and elevated bone alkaline phosphatase, compared to the HPMC group. In conclusion, topical application of HPMC/GSNO solution is a potential treatment to reduce inflammation and bone loss in periodontal disease.

Guided bone regeneration produced by new mineralized and reticulated collagen membranes in critical-sized rat calvarial defects.

The aim of this study was to evaluate the bone regenerative effect of glutaraldehyde (GA) cross-linking on mineralized polyanionic collagen membranes in critical-sized defects on rat calvarias. Bone calvarial defects were induced in Wistar rats, which were then divided into five groups: a sham group; a control group, which received a commercial membrane; and GA, 25GA, and 75GA groups, which received one of three different polyanionic collagen membranes mineralized by 0, 25, or 75 hydroxyapatite cycles and then cross-linked by GA. Bone formation was evaluated based on digital radiography and computerized tomography. Histological analyses were performed 4 and 12 weeks after the surgical procedure to observe bone formation, membrane resorption, and fibrous tissue surrounding the membranes. Measurement of myeloperoxidase activity, tumor necrosis factor alpha, and interleukin 1beta production was performed 24 h after surgery. The percentage of new bone formation in the GA, 25GA, and 75GA groups was higher compared with the control and sham groups. In the GA and 25 GA groups, the membranes were still in place and were contained in a thick fibrous capsule after 12 weeks. No significant difference was found among the groups regarding myeloperoxidase activity and interleukin 1beta levels, although the GA, 25GA, and 75GA groups presented decreased levels of tumor necrosis factor alpha compared with the control group. These new GA cross-linked membranes accelerated bone healing of the calvarium defects and did not induce inflammation. In addition, unlike the control membrane, the experimental membranes were not absorbed during the analyzed period, so they may offer advantages in large bone defects where prolonged membrane barrier functions are desirable.

S-nitrosoglutathione accelerates recovery from 5-fluorouracil-induced oral mucositis.

INTRODUCTION: Mucositis induced by anti-neoplastic drugs is an important, dose-limiting and costly side-effect of cancer therapy. AIM: To evaluate the effect of the topical application of S-nitrosoglutathione (GSNO), a nitric oxide donor, on 5-fluorouracil (5-FU)-induced oral mucositis in hamsters. MATERIALS AND METHODS: Oral mucositis was induced in male hamsters by two intraperitoneal administrations of 5-FU on the first and second days of the experiment (60 and 40 mg/kg, respectively) followed by mechanical trauma on the fourth day. Animals received saline, HPMC or HPMC/GSNO (0.1, 0.5 or 2.0 mM) 1 h prior to the 5-FU injection and twice a day for 10 or 14 days. Samples of cheek pouches were harvested for: histopathological analysis, TNF-α and IL-1ß levels, immunohistochemical staining for iNOS, TNF-α, IL-1ß, Ki67 and TGF-ß RII and a TUNEL assay. The presence and levels of 39 bacterial taxa were analyzed using the Checkerboard DNA-DNA hybridization method. The profiles of NO released from the HPMC/GSNO formulations were characterized using chemiluminescence. RESULTS: The HPMC/GSNO formulations were found to provide sustained release of NO for more than 4 h at concentration-dependent rates of 14 to 80 nmol/mL/h. Treatment with HPMC/GSNO (0.5 mM) significantly reduced mucosal damage, inflammatory alterations and cell death associated with 5-FU-induced oral mucositis on day 14 but not on day 10. HPMC/GSNO administration also reversed the inhibitory effect of 5-FU on cell proliferation on day 14. In addition, we observed that the chemotherapy significantly increased the levels and/or prevalence of several bacterial species. CONCLUSION: Topical HPMC/GSNO accelerates mucosal recovery, reduces inflammatory parameters, speeds up re-epithelization and decreases levels of periodontopathic species in mucosal ulcers.

Angiotensin II potentiates inflammatory edema in rats: Role of mast cell degranulation.

The aim of this study was to evaluate the effect of angiotensin II on models of acute inflammation. This study shows that angiotensin II potentiates the carrageenan- and dextran-induced paw edema. The administration of angiotensin II does not change the myeloperoxidase activity, neither the tissue content of interleukin-1 beta and tumor necrosis alpha nor the neutrophil migration to the peritoneal cavity, but induces significant enhancement of mast cell degranulation. The anti-histamine, mepyramine, and the anti-serotonin, metisergyde, reduce the angiotensin II-facilitated dextran-induced edema. Our results suggest that angiotensin II increases the vascular permeability through induction of mast cell degranulation and that this effect is mediated by the angiotensin AT2 receptor, since the angiotensin AT1 receptor antagonist and the angiotensin AT2 receptor agonist potentiated the paw edema.