Treating Clostridium difficile infection in patients presenting with hematological malignancies: Are current guidelines applicable?

OBJECTIVES: Adults with hematological malignancies are at high-risk of Clostridium difficile infection (CDI), but no guidelines for CDI treatment are available in this population. Our primary objective was to evaluate the clinical outcomes in CDI patients with hematological malignancies. Our secondary objectives were to describe CDI severity using the main clinical guidelines and to evaluate the compliance of treatment choice with published guidelines. PATIENTS AND METHODS: Single-center, retrospective, observational case series including every consecutive adult patient with a confirmed diagnosis of CDI admitted in the hematology unit of our teaching hospital. Each CDI episode was classified as moderate, severe, or complicated according to the main clinical guidelines (IDSA 2010, AJG 2013, ESCMID 2014). RESULTS: Twenty-three episodes of CDI in 19 patients admitted to the hematology unit occurred between June 2012 and October 2013. Clinical cure was achieved for 20 episodes (87%). Ten weeks after diagnosis, global cure was reached for 14 episodes (61%) whereas recurrence occurred in two episodes (10%). The mortality rate reached 37% (7/19) but the attributable mortality rate was 5% (1/19). ESCMID criteria more frequently classified patients in the severe category compared with the two other classifications. Prescription compliance with clinical guidelines was observed in 61% of episodes with IDSA criteria, 43% with AJG, and 9% with ESCMID. CONCLUSIONS: IDSA and AJG assessment may underestimate the potential risk of unfavorable clinical outcome. Further prospective studies on a larger cohort are needed to develop adequate treatment guidelines for CDI in hematology settings.

Cefoxitin: An alternative to carbapenems in urinary tract infections due to extended-spectrum beta-lactamase-producing Enterobacteriaceae.

BACKGROUND AND OBJECTIVES: Infections caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) have become a major public health issue worldwide. Cefoxitin is a second-generation cephalosporin and is associated with a strong in vitro activity against ESBL. PATIENTS AND METHODS: We conducted a prospective monocentric cohort study from 2012 to 2015 to evaluate the clinical efficacy and safety of cefoxitin in 15 patients treated for urinary tract infection (UTI) caused by ESBL-E, without any severity criteria. RESULTS: We included 15 patients; 11 were male patients with defined risk factors for ESBL-E. Ten patients presented with male UTI, three with pyelonephritis, and two with cystitis. Escherichia coli was the predominant pathogen. All patients had a positive outcome with a good tolerance (a skin rash without any sign of severity was observed in one patient). Microbiological cure was obtained in 9 patients out of 10 at the end of treatment. CONCLUSION: Cefoxitin is an alternative treatment to carbapenems for urinary tract infections caused by ESBL-producing Enterobacteriaceae.

Specific detection of type II human chorionic gonadotropin beta subunit produced by trophoblastic and neoplastic cells.

BACKGROUND: The sequence of the beta-subunit of human chorionic gonadotropin (hCGß) varies depending on whether hCGß is encoded by type I or type II genes. Type II genes are upregulated in trophoblast and cancer but hCGß can be detected in the serum of nonpregnant women and healthy individuals. We aimed to determine whether monoclonal antibody (mAb) FBT11-II specifically detects hCGß encoded by type II genes (type II hCGß). METHODS: Competitive inhibition assays with synthetic peptides, immunocytochemical and immunohistochemical studies, type II hCGß dosing immunoassays and sequencing of CGB genes were performed. RESULTS: Competitive inhibition assays determined that mAb FBT11-II recognizes the type II hCGß derived peptide. CGB mRNA sequencing of JEG-3 (trophoblastic) and T24 (bladder) cell lines confirmed that JEG-3 expresses type II genes while T24 expresses exclusively type I. FBT11-II only recognizes JEG-expressed hCGß. Placenta immunohistochemical studies confirmed that type II hCGß expression is restricted to the syncytiotrophoblast. Immunoassays detected type II hCGß in serum of patients with either nontrophoblastic cancers or fetal Down syndrome. CONCLUSION: Type II gene expression can be detected using FBT11-II. This specific recognition could improve the clinical usefulness of assays aimed at either managing aggressive tumors or screening for Down syndrome.

P. aeruginosa LPS stimulates calcium signaling and chloride secretion via CFTR in human bronchial epithelial cells.

BACKGROUND: Pseudomonas aeruginosa airway infection is associated with a high mortality rate in cystic fibrosis. Lipopolysaccharide (LPS), a main constituent of the outer membrane of P. aeruginosa, is responsible for activation of innate immune response but its role on airway epithelium ion transport, is not well known. The aim of this study was to determine the role for P. aeruginosa LPS in modulating chloride secretion and intracellular calcium in the human bronchial epithelial cell line, 16HBE14o-. METHODS: We used intracellular calcium imaging and short-circuit current measurement upon exposure of cells to P. aeruginosa LPS. RESULTS: Apical LPS stimulated intracellular calcium release and calcium entry and enhanced chloride secretion. This latter effect was significantly inhibited by CFTR(inh)-172 and BAPTA-AM (intracellular Ca(2+) chelator). CONCLUSIONS: Our data provides evidence for a new role of P. aeruginosa LPS in stimulating calcium entry and release and a subsequent chloride secretion via CFTR in human bronchial epithelium.

Factors associated with recurrence of catheter-related bloodstream infections in home parenteral nutrition patients.

Blood cultures from outpatients receiving home parenteral nutrition (HPN) via long-term central venous access (CVA) were retrospectively analyzed from January 2003 to May 2009. When infection of the CVA was not due to Staphylococcus aureus, Pseudomonas aeruginosa, or Candida, catheter salvage was attempted for a maximum of three consecutive infections on the same CVA. Factors influencing the time-to-next-infection were studied, whether the catheter was changed after the last infection or not. Neither the McCabe score, age, history of cancer, diabetes mellitus nor immunosuppression, curative antibiotic lock, type of bacteria, type or duration of treatment had an influence on the time-to-next-infection. The time-to-next-infection was significantly associated with the status of CVA (saved or changed) and its type (tunneled catheter with or without a cuff, or implanted port catheter).

Antibodies against glucan, chitin, and Saccharomyces cerevisiae mannan as new biomarkers of Candida albicans infection that complement tests based on C. albicans mannan.

Antibodies against Saccharomyces cerevisiae mannan (ASCA) and antibodies against synthetic disaccharide fragments of glucans (ALCA) and chitin (ACCA) are biomarkers of Crohn's disease (CD). We previously showed that Candida albicans infection generates ASCA. Here, we explored ALCA and ACCA as possible biomarkers of invasive C. albicans infection (ICI). ASCA, ALCA, ACCA, and Candida mannan antigen and antibody detection tests were performed on 69 sera obtained sequentially from 18 patients with ICIs proven by blood culture, 59 sera from CD patients, 47 sera from hospitalized subjects colonized by Candida species (CZ), and 131 sera from healthy controls (HC). ASCA, ALCA, and ACCA levels in CD and ICI patients were significantly different from those in CZ and HC subjects (P<0.0001). In ICI patients, these levels increased as infection developed. Using ASCA, ALCA, ACCA, and Platelia Candida tests, 100% of ICIs were detected, with the kinetics of the antibody response depending on the patient during the time course of infection. A large number of sera presented with more than three positive tests. This is the first evidence that the detection of antibodies against chitin and glucans has diagnostic value in fungal infections and that these tests can complement more specific tests. Future trials are necessary to assess the value of these tests in multiparametric analysis, as well as their pathophysiological relevance.

[Kinetics of Pseudomonas aeruginosa virulence gene expression during chronic lung infection in the murine model]. / Cinétique d'expression des gènes de virulence de Pseudomonas aeruginosa au cours d'une infection pulmonaire chronique dans le modèle murin.

UNLABELLED: Pseudomonas aeruginosa is a Gram-negative bacillus frequently encountered in human diseases. P. aeruginosa produces a large number of secreted and cell associated virulence factors. Their production is coordinated by various systems of gene regulation. The correlation and sequential intervention of regulation systems during a pulmonary infection have not been determined yet. OBJECTIVE: The aim of this study was to analyze the expression of three P. aeruginosa virulence genes (exoS, lasI, and algD) during the first seven days of chronic lung infection. To do so, mice were infected intratracheally with agarose beads containing P. aeruginosa. RESULTS: The results were a progressive decrease of exoS transcription and an increase of algD, and lasI transcription during infection. This dynamic evolution was consistent with the clinical observation, which demonstrated a progressive loss of type III secretion system function and an increase in the mucoid phenotype development in P. aeruginosa strains from cystic fibrosis patients. CONCLUSION: The development of a P. aeruginosa pulmonary chronic infection associates a decrease of gene expression related to a type III secretion system and an increase of alginate production.

Keratinocyte growth factor improves alterations of lung permeability and bronchial epithelium in allergic rats.

Chronic allergic asthma is associated with marked inflammatory reaction, microvascular leakage and epithelium injury. As previously shown in a rat model of chronic asthma, these alterations increase lung permeability and distal airway fluid clearance. Keratinocyte growth factor (KGF) has been shown to induce epithelial cell proliferation and to protect from acute lung injuries. Therefore, the current authors evaluated the potential role of KGF treatment on lung permeability and airway inflammation in rats with chronic asthma. KGF (1 mg x kg(-1)) was administered intravenously before the last ovalbumin (OVA) challenge in sensitised rats. Permeability was assessed by the leak of radiolabelled albumin from the alveolar and systemic compartments. Histopathological analysis was also performed. Treatment with KGF decreased the leak of both markers and decreased the level of extravascular lung water in sensitised rats challenged with OVA. KGF treatment also reduced the inflammatory cell number in bronchoalveolar lavage fluid but not in bronchial mucosa. KGF markedly limited the allergen-induced alterations in epithelium integrity and the expression of the intercellular junction proteins beta-catenin and zonula occludens protein-1. In conclusion, keratinocyte growth factor administration markedly limits lung permeability and airway inflammation, an effect associated with a decrease in epithelium alterations during chronic allergic asthma. These data open new prospects in the therapeutic strategy of asthma.

[Acute invasive pulmonary aspergillosis in chronic lung disease--a review]. / Aspergillose pulmonaire aiguë invasive et pathologies pulmonaires chroniques.

INTRODUCTION: Apart from malignancies and solid organ transplant, chronic lung disease, in particular chronic obstructive pulmonary disease (COPD), is a third important predisposing factor for acute invasive pulmonary aspergillosis. STATE OF THE ART: COPD is present in 2% of patients dying from invasive aspergillosis. This opportunistic infection occurs because of an immunodeficiency linked both to altered local immunity and to systemic factors such as long term steroid treatment and malnutrition. In patients whose sputum and/or endotracheal aspirate specimens contain hyphal forms of filamentous Aspergillus, half will have a clinically significant aspergillus infection. Diagnostic tests include serum galactomannan antigen test, serum antibody titre, thoracic CT scan and bronchoalveolar lavage (BAL). The identification of fungal hyphae in BAL fluid by microscopy and/or on culture is critical for a positive diagnosis. The mortality rate for acute invasive pulmonary aspergillosis in chronic lung diseases reaches almost 100%. Antifungal monotherapy is still recommended as a first line treatment. Combined treatment can be used in refractory aspergillosis as a salvage therapy. The question of maintaining, decreasing or interrupting steroid treatment must be considered. PERSPECTIVES: Prospective studies are needed to evaluate a standardised diagnostic strategy such as exists for patients with haematological disease. Whether this will improve prognosis remains to be seen. CONCLUSION: Acute invasive pulmonary aspergillosis complicating chronic lung disease is not rare. Improved diagnosis procedures and recent therapeutic advances may have a positive impact on patient prognosis.

[Pseudomonas aeruginosa and Surfactant-associated Proteins A and D]. / Pseudomonas aeruginosa et surfactant rôle de SP-A et SP-D.

Surfactant-associated proteins A and D (SP-A and SP-D) are two pulmonary collectins that bind to bacterial, fungal and viral pathogens and have multiples classes of receptors on pneumocyte and macrophage membrane. They are chemoattractant for phagocytes, enhance uptake and killing of bacteria by macrophages and neutrophils. These molecules also act as activation ligand on macrophages and neutrophils to enhance phagocytosis, resulting in an increased bacterial clearance. Depending on activation of cells by stimuli, SP-A and SP-D modulate production of antimicrobial free radicals by phagocytes and secretion of cytokines. In vivo, SP-A deficient mice infected with Pseudomonas aeruginosa (P. aeruginosa) have decreased bacterial clearance and exacerbated inflammatory response in the lungs. Serious alterations in macrophages and increased production of reactive oxygen species were found in non-infected SP-D deficient mice. Patients with cystic fibrosis are frequently colonized by P. aeruginosa. Decreased levels of SP-A and SP-D have been measured in bronchoalveolar lavage fluid of these patients, as well as patients with acute pneumonia but no chronic lung disease. P. aeruginosa secretes various proteases, among them, elastase and protease IV have been found to degrade SP-A and SP-D and abrogate their immune function. However, further investigations are necessary to examine whether these deficiencies facilitate P. aeruginosa infections or stand as consequences.

Alveolar response to Pseudomonas aeruginosa: role of the type III secretion system.

The type III secretion system (TTSS) is a specialized cytotoxin-translocating apparatus of gram-negative bacteria which is involved in lung injury, septic shock, and a poor patient outcome. Recent studies have attributed these effects mainly to the ExoU effector protein. However, few studies have focused on the ExoU-independent pathogenicity of the TTSS. For the present study, we compared the pathogenicities of two strains of Pseudomonas aeruginosa in a murine model of acute lung injury. We compared the CHA strain, which has a functional TTSS producing ExoS and ExoT but not ExoU, to an isogenic mutant with an inactivated exsA gene, CHA-D1, which does not express the TTSS at all. Rats challenged with CHA had significantly increased lung injury, as assessed by the wet/dry weight ratio for the lungs and the protein level in bronchoalveolar lavage fluid (BALF) at 12 h, compared to those challenged with CHA-D1. Consistent with these findings, the CHA strain was associated with increased in vitro cytotoxicity on A549 cells, as assessed by the release of lactate dehydrogenase. CHA was also associated at 12 h with a major decrease in polymorphonuclear neutrophils in BALF, with a proinflammatory response, as assessed by the amounts of tumor necrosis factor alpha and interleukin-1beta, and with decreased bacterial clearance from the lungs, ultimately leading to an increased mortality rate. These results demonstrate that the TTSS has a major role in P. aeruginosa pathogenicity independent of the role of ExoU. This report underscores the crucial roles of ExoS and ExoT or other TTSS-related virulence factors in addition to ExoU.

[Surgical antimicrobial prophylaxis: compliance to guidelines and impact of targeted information program]. / Antibioprophylaxie chirurgicale: adéquation aux recommandations et impact d'une action d'information ciblée.

OBJECTIVES: Surgical antimicrobial prophylaxis is used to decrease postoperative wound infection. We assessed the compliance to surgical antimicrobial prophylaxis guidelines in our hospital and the impact of an information program. PATIENTS AND METHODS: Observational study of clean or clean contamined surgery, during two 3-week periods, separated by a targeted information period. The following data were collected prospectively: prophylaxis indication, antimicrobial agent, timing, dose, route and duration of prophylaxis. Chi square test was used for analysis or Fischer test when available. RESULTS: Four hundred seventy-seven patients were enrolled - 270 and 207 for each period respectively. For both periods only 49% of prophylaxis was appropriated. When prophylaxis should be administered - 15 and 13% of patients for each period - it was antibioprophylaxy was strictly adequate with recommandations. The most common error was administration timing. Only the choice of antimicrobial agent was optimized after information period. DISCUSSION: These results are consistent with previous studies. Information program alone have no effect on the good use of antimicrobial for surgical prophylaxis. Only a policy associating organization, restriction and education could improve practices.

[Viral pneumonia in immunocompetent patients]. / Pneumonie virale sévère de l'immunocompétent.

Respiratory infections are frequently encountered in the community; these infections are usually associated with only minor consequences. Many different agents, such as influenza and parainfluenza virus, respiratory syncitial virus, rhinovirus, coronavirus, adenovirus and herpes virus can be found in immuno-competent patients. Among these pathogens, cytomegalovirus (CMV) has been found to be responsible for nosocomial pneumonia in ICU. The main problem for viral infections, is the diagnosis, isolation of the pathogen is often difficult and not always reliable and the symptoms not specific. However, influenza is characterised by fever, myalgia, headache and pharyngitis, this infection may be very mild, even asymptomatic, moderate or very severe. Finally, the most recent viral pathogen involved in respiratory disease is a newly discovered coronavirus, the SARS-CoV which was responsible for the worldwide outbreak of Severe Acute Respiratory Syndrome. Viral pneumonia is a common pathology which is probably underdiagnosed in immuno-competent patients; many reports show that even if the diagnosis is difficult to obtain, it is not useless as long as we have, for most of the pathogens, an effective treatment. The gold standard was histology, new techniques like PCR can probably make a difference and should be included in the guidelines to improve diagnostic efficiency.

Keratinocyte growth factor (KGF) decreases ICAM-1 and VCAM-1 cell expression on bronchial epithelial cells.

Activation of leucocytes during airway inflammatory reaction involves adhesion to bronchial epithelial cells (BEC), a process implicating specific interactions between glycoproteins with epithelial cell surface proteins, mainly intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). In this study, the effect of keratinocyte growth factor (KGF), a growth factor involved in pulmonary epithelium repair, was evaluated on adhesion molecule expression with BEAS-2B cells and BEC and granulocyte adherence to BEAS-2B. The modulation by KGF of membrane and mRNA expression of ICAM-1 and VCAM-1 was studied on confluent cells stimulated or not with tumour necrosis factor-alpha (TNF) (200 UI/ml) or TNF and interleukin (IL)-4 (50 UI/ml and 10 ng/ml). Levels of soluble-(s)ICAM-1 and sVCAM-1 were measured by ELISA. Although moderately, KGF significantly decreased membrane ICAM-1 expression in unstimulated BEAS-2B cells (24% inhibition at 100 ng/ml) or in TNF- or TNF + IL-4-stimulated cells (22.5 and 18.7% inhibition, respectively). Treatment with KGF tended to decrease VCAM-1 expression in TNF- and TNF + IL-4-stimulated BEAS-2B (P = n.s. and P < 0.05, 14 and 15% inhibition, respectively). In primary culture of BEC, adhesion molecule expression was also reduced. ICAM-1 and VCAM-1 mRNA expression were also inhibited by KGF. Levels of sICAM-1 and sVCAM-1 were not significantly increased in supernatants from KGF-treated cells (30% and 24% increase at 100 ng/ml, respectively) compared to controls. Moreover, KGF decreased by 31% the adherence of neutrophils to TNF-activated BEAS-2B. In conclusion, KGF decreases ICAM-1 and VCAM-1 expression and neutrophil adherence in BEC. These suggest its involvement in the resolution of the inflammatory reaction.

[Revascularization of atherosclerotic stenosis of the renal artery. Indications and results]. / Revascularisation des sténoses athéroscléreuses de l'artère rénale. Indications et résultats.

RISKS: Atherosclerotic renal artery stenosis typically occurs in high risk patients with coexistent vascular disease elsewhere. Patients with atherosclerotic renal artery stenosis may develop progressive renal failure but have a much higher risk of dying with a stroke or a myocardial infarction than of progressing to end-stage renal disease. REVASCULARIZATION RESULTS: Recent controlled trials comparing medication to revascularization have shown that only a minority of such patients can expect hypertension cure, whereas trials designed to document the ability of revascularization to prevent progressive renal failure are not yet available. Percutaneous renal artery angioplasty is the first choice because it is simpler than and as effective as surgical reconstruction. INDICATIONS: Revascularization should be undertaken in patients with atherosclerotic renal artery stenosis and resistant hypertension or heart failure, and probably in those with rapidly deteriorating renal function or with an increase in plasma creatinine levels during angiotensin-converting enzyme inhibition. Older age, long history of hypertension and a kidney size less than 8 cm are associated with little chance of blood pressure improvement or kidney function recovery. PRACTICAL ATTITUDE: With or without revascularization, medical therapy using antihypertensive agents, statins and aspirin is necessary in almost all cases. Blood pressure and plasma creatinine concentration should be measured every three months. Kidney size and renal artery patency should be assessed yearly.

Presentation and revascularization outcomes in patients with radiation-induced renal artery stenosis.

This study analyzed the initial presentation and revascularization outcomes of patients with radiation-induced renal artery stenosis, a rare complication of therapeutic irradiation. Of 11 patients with renal artery stenosis after irradiation, 7 patients fulfilled the following criteria: normotension before irradiation, radiation dose greater than 25 grays delivered to the renal arteries, associated perirenal radiation-induced lesions, and absence of arterial disease outside the radiation field. The median age at irradiation was 30 years, and the median local irradiation dose was 40 grays. The median time from irradiation to referral was 13 years. All patients were hypertensive at referral, with a median blood pressure (BP) of 171/102 mm Hg and median treatment score of two. The median glomerular filtration rate was 67 mL/min. Two patients had bilateral stenoses and 1 patient had stenosis affecting a single kidney. Stenoses were proximal in 6 patients and truncal in 1 patient, and all had the appearance of atherosclerotic stenosis. Percutaneous transluminal renal artery angioplasty (PTRA) was successful in 5 patients, but required multiple insufflations. PTRA failed in 1 patient, who subsequently underwent an aortorenal bypass. After a median follow-up of 36 months, 2 patients had died of noncardiovascular causes and 4 patients remained hypertensive, with a median BP of 136/85 mm Hg and median treatment score of two. No restenosis occurred, but aneurysms developed at the site of angioplasty in 1 patient. If hypertension occurs even decades after irradiation, a radiation-induced renal artery stenosis should be sought in patients who have undergone abdominal irradiation.

Atherosclerotic renal artery stenosis: surgery, percutaneous transluminal angioplasty, or medical therapy?

Atherosclerotic renal artery stenosis typically occurs in high-risk patients with coexistent vascular disease elsewhere. Patients with atherosclerotic renal artery stenosis may develop progressive renal failure but have a much higher risk of dying of stroke or myocardial infarction than of progressing to endstage renal disease. Recent controlled trials comparing medication to revascularization have shown that only a minority of such patients can expect hypertension cure, whereas trials designed to document the ability of revascularization to prevent progressive renal failure are not yet available. Revascularization should be undertaken in patients with atherosclerotic renal artery stenosis and resistant hypertension or heart failure, and probably in those with rapidly deteriorating renal function or an increase in plasma creatinine levels during angiotensin converting enzyme inhibition. With or without revascularization, medical therapy using antihypertensive agents, statins, and aspirin is necessary in almost all cases.

[Hypertension and primary hyperaldosteronism]. / Hypertension artérielle des hyperaldostéronismes primaires.

Hypokalaemic hypertension or resistant hypertension justify investigation for primary hyperaldosteronism. The first step of this investigation is to exclude the ingestion of liquorice, alkalis and diuretics. The second is to make sure that the treatment is compatible with the hormonal tests and that the natriuresis and kaliuresis are normal. The diagnosis then depends on an increased plasma or urinary concentration of aldosterone with a low plasma renin activity. The adenoma of Conn is present in 2/3 of cases and surgically curable, and should be distinguished from adrenal hyperplasia which is treatable with distal diuretics. This is a diagnosis which requires computerised tomography or, when inconclusive, demonstration of unilateral secretion of aldosterone. Adrenalectomy, usually by coelioscopy, is indicated in Conn's adenoma when the patient is young and the hypertension severe or recent. Surgical abstention is strongly advised in cases of adrenal hyperplasia.

Inhaled NO preadministration modulates local and remote ischemia-reperfusion organ injury in a rat model.

Inhaled nitric oxide (iNO) has been shown to have a protective effect in lung ischemia-reperfusion (I/R)-induced injuries. We studied the role of iNO (10 parts/million for 4 h) administered before I/R. In an isolated perfused lung preparation, iNO decreased the extravascular albumin accumulation from 2,059 +/- 522 to 615 +/- 105 microl and prevented the increase in lung wet-to-dry weight ratio. To study the mechanisms of this prevention, we evaluated the role of nitric oxide (NO) transport and lung exposure with matched experiments by using either lungs or blood of animals exposed to iNO and blood or lungs of naive animals. iNO-exposed blood with naive lungs did not limit the extravascular albumin accumulation (2,561 +/- 397 microl), but iNO-exposed lungs showed a leak not significantly different from the group in which both lungs and blood were iNO exposed (855 +/- 224 vs. 615 +/- 105 microl). An improvement in heart I/R left ventricular developed pressure in the animals exposed to iNO showed that blood-transported NO was, however, sufficient to trigger remote organ endothelium and reduce the consequences of a delayed injury. In conclusion, preventive iNO reduces the consequences of lung I/R injuries by a mechanism based on tissue or endothelium triggering.