A total of 4352 patients were admitted to a prospective' randomised multicentre trial comparing the prophylactic efficacy of dextran 70 and low-dose heparin against fatal pulmonary embolism after elective operations for general, orthopaedic, urological, and gynaecological conditions. Out of 3984 patients correctly admitted, 1993 were allocated to receive dextran 70 and 1991 to receive low-dose heparin. Withdrawal of prophylaxis because of bleeding or technical difficulties occurred more often in the heparin group, but allergic reactions were more common in the dextran group. Of the 75 patients who died within 30 days after operation, 38 had been given dextran and 37 low-dose heparin. Necropsy was performed in 33 and 32 of these cases respectively. In six patients in each group pulmonary embolism was the sole or a contributory cause of death. Of these, five patients in the dextran group and two in the heparin group had received a full course of prophylaxis. There was no statistically significant difference between the two treatment groups in the incidence of fatal pulmonary embolism after a full course of prophylaxis.

A method for intravital microscopy studies of macromolecular permeability is described. The cheek pouch of an anaesthetized hamster was everted and a single layer preparation was mounted on a microscope stage and dissected during observation with a stereomicroscope at 10–16 times magnification. The cheek pouch preparation was superfused with a buffered electrolyte solution with pH=7.35 at 37°C and with a PO₂<4kPa (<30 mmHg). Fluorescein labelled dextran ω_w,=145000 (FITC-dextran 145) was used as a tracer for permeability. Sites of microvascular permeability to macromolecules were indicated by extravasation of FITC-dextran 145. Leakage of this tracer from the microcirculation was found to occur at the postcapillary venules only. The number of FITC-dextran leakage sites was used for quantitation of the permeability during intravital observations in untreated control and indomethacin-treated hamsters. The number of leakage sites was significantly increased at 120 min in control hamsters but not until 300 min in the indomethacin-treated hamsters. There was a significant difference in permeability at 120 min in control hamsters as compared to indomethacin-treated. Analysis of PGE₂-activity in pooled samples of exposed cheek pouches at 5 hours showed 20 times higher activity in these pouches when compared to the unexposed pouches. Indomethacin was found to inhibit PGE₂-synthesis and to reduce the number of leaking postcapillary venules. The model allows studies on the dynamics of macromolecular transport in the microvasculature and its relation to other vascular parameters such as vessel diameter and blood flow. It should also be useful for studies of inflammatory and immunological responses in the microcirculation and the pharmacology of small vessel permeability to macromolecules.

We have previously reported that exogenous bradykinin activates immature dendritic cells (DCs) via the bradykinin B₂ receptor (B₂R), thereby stimulating adaptive immunity. In this study, we show that these premises are met in a model of s.c. infection by Trypanosoma cruzi, a protozoan that liberates kinins from kininogens through its major protease, cruzipain. Intensity of B₂R-dependent paw edema evoked by trypomastigotes correlated with levels of IL-12 produced by CD11c⁺ dendritic cells isolated from draining lymph nodes. The IL-12 response induced by endogenously released kinins was vigorously increased in infected mice pretreated with inhibitors of angiotensin converting enzyme (ACE), a kinin-degrading metallopeptidase. Furthermore, these innate stimulatory effects were linked to B₂R-dependent up-regulation of IFN-γ production by Ag-specific T cells. Strikingly, the trypomastigotes failed to up-regulate type 1 immunity in TLR2^−/− mice, irrespective of ACE inhibitor treatment. Analysis of the dynamics of inflammation revealed that TLR2 triggering by glycosylphosphatidylinositol-anchored mucins induces plasma extravasation, thereby favoring peripheral accumulation of kininogens in sites of infection. Further downstream, the parasites generate high levels of innate kinin signals in peripheral tissues through the activity of cruzipain. The demonstration that the deficient type 1 immune responses of TLR2^−/− mice are rescued upon s.c. injection of exogenous kininogens, along with trypomastigotes, supports the notion that generation of kinin “danger” signals is intensified through cooperative activation of TLR2 and B₂R. In summary, we have described a s.c. infection model where type 1 immunity is vigorously up-regulated by bradykinin, an innate signal whose levels in peripheral tissues are controlled by an intricate interplay of TLR2, B₂R, and ACE.

BACKGROUND AND PURPOSE Independent studies in experimental models of Trypanosoma cruzi appointed different roles for endothelin‐1 (ET‐1) and bradykinin (BK) in the immunopathogenesis of Chagas disease. Here, we addressed the hypothesis that pathogenic outcome is influenced by functional interplay between endothelin receptors (ET_AR and ET_BR) and bradykinin B₂ receptors (B₂R).EXPERIMENTAL APPROACH Intravital microscopy was used to determine whether ETR/B₂R drives the accumulation of rhodamine‐labelled leucocytes in the hamster cheek pouch (HCP). Inflammatory oedema was measured in the infected BALB/c paw of mice. Parasite invasion was assessed in CHO over‐expressing ETRs, mouse cardiomyocytes, endothelium (human umbilical vein endothelial cells) or smooth muscle cells (HSMCs), in the presence/absence of antagonists of B₂R (HOE‐140), ET_AR (BQ‐123) and ET_BR (BQ‐788), specific IgG antibodies to each GPCRs; cholesterol or calcium‐depleting drugs. RNA interference (ET_AR or ET_BR genes) in parasite infectivity was investigated in HSMCs.KEY RESULTS BQ‐123, BQ‐788 and HOE‐140 reduced leucocyte accumulation in HCP topically exposed to trypomastigotes and blocked inflammatory oedema in infected mice. Acting synergistically, ET_AR and ET_BR antagonists reduced parasite invasion of HSMCs to the same extent as HOE‐140. Exogenous ET‐1 potentiated T. cruzi uptake by HSMCs via ETRs/B₂R, whereas RNA interference of ET_AR and ET_BR genes conversely reduced parasite internalization. ETRs/B₂R‐driven infection in HSMCs was reduced in HSMC pretreated with methyl‐β‐cyclodextrin, a cholesterol‐depleting drug, or in thapsigargin‐ or verapamil‐treated target cells.CONCLUSIONS AND IMPLICATIONS Our findings suggest that plasma leakage, a neutrophil‐driven inflammatory response evoked by trypomastigotes via the kinin/endothelin pathways, may offer a window of opportunity for enhanced parasite invasion of cardiovascular cells.LINKED ARTICLE This paper is commented on by D'Orléans‐Juste et al., pp. 1330–1332 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476‐5381.2011.01636.x

Porphyromonas gingivalis, a Gram-negative bacterium that causes periodontitis, activates the kinin system via the cysteine protease R-gingipain. Using a model of buccal infection based on P. gingivalis inoculation in the anterior mandibular vestibule, we studied whether kinins released by gingipain may link mucosal inflammation to T cell-dependent immunity through the activation of bradykinin B₂ receptors (B₂R). Our data show that P. gingivalis W83 (wild type), but not gingipain-deficient mutant or wild-type bacteria pretreated with gingipain inhibitors, elicited buccal edema and gingivitis in BALB/c or C57BL/6 mice. Studies in TLR2^−/−, B₂R^−/−, and neutrophil-depleted C57BL/6 mice revealed that P. gingivalis induced edema through the sequential activation of TLR2/neutrophils, with the initial plasma leakage being amplified by gingipain-dependent release of vasoactive kinins from plasma-borne kininogens. We then used fimbriae (Fim) Ag as a readout to verify whether activation of the TLR2→PMN→B₂R axis (where PMN is polymorphonuclear neutrophil) at early stages of mucosal infection had impact on adaptive immunity. Analyzes of T cell recall responses indicated that gingipain drives B₂R-dependent generation of IFN-γ-producing Fim T cells in submandibular draining lymph nodes of BALB/c and C57BL/6 mice, whereas IL-17-producing Fim T cells were generated only in BALB/c mice. In summary, our studies suggest that two virulence factors, LPS (an atypical TLR2 ligand) and gingipain, forge a trans-cellular cross-talk between TLR2 and B₂R, thus forming an innate axis that guides the development of Fim-specific T cells in mice challenged intrabuccally by P. gingivalis. Ongoing research may clarify whether kinin-driven modulation of T cell responses may also influence the severity of chronic periodontitis.