Mechanism by which methylprednisolone inhibits acute immune complex-induced changes in vascular permeability

Asthma is not only an airway disease, but also a vascular disease

Multiple studies have identified an expansion and morphological dysregulation of the bronchial vascular network in the airways of asthmatics. Increased number, size and density of blood vessels, as well as vascular leakage and plasma engorgement, have been reported in the airways of patients with all grades of asthma from mild to fatal. This neovascularisation is an increasingly commonly reported feature of airway remodelling; however, the pathophysiological impact of the increased vasculature in the bronchial wall and its significance to pulmonary function in asthma are unrecognised at this time. Multiple factors capable of influencing the development and persistence of the vascular network exist within asthmatic airway tissue. These include structural components of the altered extracellular matrix (ECM), imbalance of proteases and their endogenous inhibitors, release of active matrikines and the dysregulated levels of both soluble and matrix sequestered growth factors. This review will explore the features of the asthmatic airway which influence the development and persistence of the increased vascular network, as well as the effect of enhanced tissue perfusion on chronic inflammation and airway dynamics. The response of cells of the airways to the altered vascular profile and the subsequent influence on the features of airway remodelling will also be highlighted. We will explore the failure of current asthma therapeutics in "normalising" this vascular remodelling. Finally, we will summarize the outcomes of recent clinical trials which provide hope that anti-angiogenic therapies may be a potent asthma-resolving class of drugs and provide a new approach to asthma management in the future.

AIT-082 and methylprednisolone singly, but not in combination, enhance functional and histological improvement after acute spinal cord injury in rats

Extracellular non-adenine based purines are neuroprotective. Preliminary studies indicate that administration of the synthetic purine 4-[[3-(1,6 dihydro-6-oxo-9-purine-9-yl)-1-oxypropyl] amino] benzoic acid (AIT-082, leteprinim potassium) to rats immediately after acute spinal cord injury (SCI), improves functional outcome. The effects of potential new agents are often compared to methylprednisolone (MPSS). We evaluated the effects of AIT-082 and MPSS, separately and in combination, on the functional and morphological outcome of acute SCI in adult rats. After standardized T11-12 spinal cord compression rats were given intraperitoneally one of the following: vehicle (saline); MPSS (30 mg/kg or 60 mg/kg body weight, first dose 15 min after crush); AIT-082 (60 mg/kg body weight daily, first dose 15 min after crush); or AIT-082 plus MPSS. After 1, 3, or 21 days, the rats were perfused for histological analysis. AIT-082 administrations significantly reduced locomotor impairment from 121 days post-operatively. At 1 and 3 days post injury, AIT-082-treatment reduced tissue swelling, tissue loss and astrogliosis at the injured cords but did not alter the extent of hemorrhage and the number of macrophages and/or microglia. MPSS reduced hemorrhage and the number of macrophages and/or microglia, but did not alter astrogliosis. At 21 days, either AIT-082 or MPSS administration improved function and morphology similarly (less tissue loss and astrogliosis). In contrast, administration of AIT-082 and MPSS together abolished the beneficial effects observed when either drug was given individually. These results suggest that MPSS and AIT-082 may exert their beneficial effects through different and potentially antagonistic pathways.

Oxidative stress in expired breath condensate of patients with COPD

OBJECTIVE

To evaluate the levels of hydrogen peroxide (H(2)O(2)) and 8-isoprostane in the expired breath condensate (EBC) of patients with COPD, and to assess the relationship between the above markers of oxidative stress and parameters expressing inflammatory process and disease severity.

SETTING

Inpatient respiratory unit and outpatient clinic in tertiary care hospital.

DESIGN

Cross-sectional study.

PATIENTS

Thirty stable COPD patients (all smokers) with disease severity ranging from mild to severe. Ten subjects who were smokers with stage 0 disease (ie, at risk for COPD; mean [+/- SD] FEV(1), 88 +/- 5% predicted) were studied as a control group.

METHODS

H(2)O(2) and 8-isoprostane levels were measured in EBC, and the values were correlated with variables expressing COPD severity (ie, FEV(1) percent predicted, dyspnea severity score (ie, Medical Research Council scale) and airway inflammation (ie, differential cell counts from induced sputum).

RESULTS

The mean concentration of H(2)O(2) was significantly elevated in COPD patients compared to control subjects (mean, 0.66 micromol/L [95% confidence interval (CI), 0.54 to 0.68 micro mol/L) vs 0.31 micro mol/L [95% CI, 0.26 to 0.35 micromol/L], respectively; p < 0.0001). The difference was primarily due to the elevation of H(2)O(2) in patients with severe and moderate COPD, whose expired breath H(2)O(2) levels were significantly higher than those of patients with mild disease (mean, 0.96 micromol/L [95% CI, 0.79 to 1.13 micromol/L], 0.68 micromol/L [95% CI, 0.55 to 0.81 micromol/L], and 0.33 micromol/L [95% CI, 0.24 to 0.43 micromol/L], respectively, p < 0.0001). The mean concentration of 8-isoprostane was significantly elevated in patients with COPD compared to that of the control group (47 pg/mL [95% CI, 41 to 53 pg/mL] vs 29 pg/mL [95% CI, 25 to 33 pg/mL], respectively; p < 0.0001) but did not differ significantly among the different stages of the disease (p = 0.43). Repeatability and stability data within measurements showed that H(2)O(2) has a better repeatability and stability than 8-isoprostane. Furthermore, we observed significant correlations of H(2)O(2) with FEV(1), neutrophil count, and dyspnea score. Those correlations existed only in patients with moderate and severe disease. No correlations were found between levels of 8-isoprostane and the above parameters.

CONCLUSIONS

We conclude that levels of H(2)O(2) and 8-isoprostane are elevated in the EBC of patients with COPD, but that H(2)O(2) seems to be a more repeatable and a more sensitive index of the inflammatory process and the severity of the disease.

The relationships among hydrogen peroxide in expired breath condensate, airway inflammation, and asthma severity

STUDY OBJECTIVE

To investigate which cells are the main source of hydrogen peroxide (H(2)O(2)) production in stable patients with asthma and the associations among H(2)O(2) levels, airway inflammation, and disease severity.

SETTING

Inpatient respiratory unit and outpatient clinic in tertiary-care hospital.

PATIENTS

Fifty stable asthmatic patients with disease severity ranging from mild to moderate.

METHODS

H(2)O(2) was measured in expired breath condensate and was correlated with variables expressing both asthma severity (ie, FEV(1) percent predicted, peak expiratory flow rate [PEFR] variability, symptom score, and histamine airways responsiveness) and airway inflammation (ie, differential cell counts from induced sputum and levels of eosinophil cationic protein [ECP]).

RESULTS

The mean (95% confidence interval [CI]) concentration of H(2)O(2) was significantly elevated in patients with asthma compared to that in control subjects (mean, 0.67 microM [95% CI, 0.56 to 0.77 microM] vs 0.2 microM [95% CI, 0.16 to 0.24 microM]; p < 0.0001). The difference was primarily due to the elevation of H(2)O(2) in patients with moderate asthma whose expired breath H(2)O(2) level of 0.95 microM (95% CI, 0.76 to 1.12 microM) was significantly higher from that of patients with mild-persistent and mild-intermittent asthma (mean, 0.59 microM [95% CI, 0.47 to 0.7 microM] and 0.27 [95% CI, 0.23 to 0.32 microM], respectively; p < 0.0001). H(2)O(2) concentration was positively related to sputum eosinophilia as well as to ECP concentration. A similar correlation was found between H(2)O(2) and neutrophils in patients with moderate asthma. A positive correlation was observed between H(2)O(2) level, symptom score, and PEFR variability. H(2)O(2) level was negatively related to FEV(1) percent predicted. Further analysis showed that only patients with moderate asthma who were not receiving inhaled steroids were found to have a strong relationship with the variables tested.

CONCLUSIONS

Eosinophils are the predominate cells that generate H(2)O(2) in all forms of the disease, while neutrophils might be responsible for the highest levels that are observed in the more severe forms of the disease. The role of H(2)O(2) concentration in predicting the severity of the disease as well as in the inflammatory process is limited and depends on the use of inhaled steroid therapy and the classification of the severity of the disease.

Exhaled H(2)O(2) in steady-state bronchiectasis: relationship with cellular composition in induced sputum, spirometry, and extent and severity of disease

STUDY OBJECTIVES

To determine the concentration of exhaled H(2)O(2) in patients with bronchiectasis, and to study the relationship between levels of exhaled H(2)O(2), extent of disease, symptoms score, spirometry, and cellular composition obtained from induced sputum; furthermore, to account for possible confounding effects of inhaled corticosteroids (ICS) usage, long-term oral antibiotic treatment, and chronic colonization with Pseudomonas aeruginosa.

DESIGN

Cross-sectional study.

PATIENTS

Thirty patients with steady-state bronchiectasis.

RESULTS

Mean (95% confidence interval [CI]) exhaled H(2)O(2) levels were significantly elevated in patients with bronchiectasis compared to normal subjects: 1.1 (0.87 to 1.29) microM vs 0.3 (0.19 to 0.36) microM, respectively (p < 0.0001). Patients treated with ICS had similar values as steroid-naïve patients. The group of patients with P aeruginosa colonization showed a significantly increased concentration of H(2)O(2) compared to the group without P aeruginosa colonization. Patients receiving long-term oral antibiotic treatment had significantly higher values of H(2)O(2) compared to those not receiving antibiotics. There was a significant positive correlation between H(2)O(2) and either the percentage of neutrophils in induced sputum or the extent of the disease as defined by high-resolution CT. A significant negative correlation was found between H(2)O(2) and FEV(1) percent predicted. Finally, there was a significant positive correlation between H(2)O(2) and the symptoms score.

CONCLUSIONS

Patients with bronchiectasis in stable condition showed increased levels of exhaled H(2)O(2). The above-mentioned levels were not decreased either by ICS or long-term oral antibiotic treatment, but were significantly affected by chronic colonization with P aeruginosa. H(2)O(2) levels could be an indirect index of neutrophilic inflammation, impairment of lung function, and extension and severity of the disease.

Inhaled corticosteroids decrease vascularity of the bronchial mucosa in patients with asthma

BACKGROUND

Increased vascularity in airway mucosa is a distinctive feature of airway remodelling in asthma. While corticosteroids have proved most effective in modifying airway inflammation, the effect of inhaled corticosteroids on increased airway mucosal vascularity in asthmatics has been little studied.

OBJECTIVE

We examined the effect of inhaled corticosteroid on airway vascularity in bronchial biopsy specimens taken from asthmatic patients.

SUBJECTS AND METHODS

We studied bronchial biopsies from 28 asthmatic patients before and after treatment with inhaled beclomethasone dipropionate (BDP) 800 microg/daily, or placebo, for 6 months in a double-blind manner. Biopsy specimens were evaluated for number of vessels and percentage of area occupied by vessels, using computerized image analysis after staining for type IV collagen in vessel walls. Specimens were also examined for extent of collagen III in the subepithelial basement membrane. In addition, we compared asthmatic specimens with biopsy specimens taken from non-asthmatic control subjects.

RESULTS

There was a significant increase in number of vessels (P < 0.01) and percent vascularity (P < 0.001) in the submucosa of asthmatic patients compared with control subjects. After 6 months of treatment, we observed significant improvements in forced expiratory volume in 1 s (FEV1), FEV1% and airway responsiveness (P < 0.05, each) in the BDP treatment group compared with the placebo group. This was accompanied by significant decreases in both vessel number and percent vascularity in the airways of BDP-treated patients (P < 0.05, each). We also observed a significant correlation between change in percent vascularity and change in collagen III thickness in the BDP-treated patients (rs = 0.90, P < 0.001). Furthermore, the change in percent vascularity was inversely correlated with both FEV1 (rs = -0.49, P < 0.05) and airway responsiveness (rs = -0.36, P < 0.05).

CONCLUSION

These findings suggest that inhaled corticosteroid treatment of asthma reduced airway wall vascularity during airway remodelling.

Vascularity in asthmatic airways: relation to inhaled steroid dose

BACKGROUND

There is an increase in vascularity in the asthmatic airway. Although inhaled corticosteroids (ICS) are an effective anti-inflammatory treatment in asthma, there are few data on any effects on structural changes.

METHODS

Endobronchial biopsy specimens from seven asthmatic subjects not receiving ICS and 15 receiving 200-1500 microg/day beclomethasone dipropionate (BDP) were immunohistochemically stained with an anti-collagen type IV antibody to outline the endothelial basement membrane of the vessels. These were compared with biopsy tissue from 11 non-asthmatic controls (four atopic and seven non-atopic).

RESULTS

There was a significant increase in the density of vessels (number of vessels/mm2 of lamina propria) in the asthmatic subjects not on ICS compared with non-asthmatic controls (mean 485 (interquartile range (IQR) 390-597) versus 329 (IQR 248-376) vessels/mm2, p<0.05; 95% CI for the difference 48 to 286). There was no significant difference between asthmatic subjects on ICS and those not on ICS or control subjects in the number of vessels/mm2 (mean 421 (IQR 281-534)). However, patients who received >/=800 microg/day BDP tended to have a reduced number of vessels/mm2 compared with patients not on ICS and those receiving </=500 microg/day BDP (mean 366 (IQR 153-608) versus 494 (IQR 391-583), p = 0.08; 95% CI for the difference -31 to 288). Similarly, there was an increase in the percentage of lamina propria occupied by vessels in asthmatic patients not on ICS compared with controls (mean 15.6% (IQR 13.1-18.0) versus 10.1% (IQR 8.4-13.3), p<0.01; 95% CI for the difference 2.4 to 9.3) but a significant decrease in the percentage of lamina propria occupied by vessels was detected in asthmatic patients on ICS (mean 11.4% (IQR 9.1-14.9), p<0.01; 95% CI for the difference 0.7 to 7.7) compared with those not on ICS. The density of vessels correlated significantly with both airway hyperresponsiveness and percentage change in forced expiratory volume in one second (FEV1) after bronchodilator (r = -0. 38 for PD20 methacholine and r = 0.49 for change in percentage FEV1 after bronchodilator versus number of vessels/mm2, p<0.05).

CONCLUSION

These findings suggest that ICS, especially at higher doses, may reduce airway wall vascularity in asthmatic subjects but further longitudinal intervention studies are required to confirm this suggestion.

Elevated levels of expired breath hydrogen peroxide in bronchiectasis

Airway inflammation is important in the development and progression of many lung diseases, including bronchiectasis. Activation of inflammatory cells such as neutrophils, eosinophils, and macrophages induces a respiratory burst resulting in the production of reactive oxygen species such as hydrogen peroxide (H2O2). We have measured exhaled H2O2 in patients with documented bronchiectasis and investigated whether the concentration of H2O2 is related to the disease severity, as defined by lung function. We also investigated whether the concentrations of expired H2O2 were different in bronchiectatic patients who received inhaled corticosteroids compared with steroid-naïve patients. In 37 patients with bronchiectasis (mean age, 45 +/- 2.5 yr; FEV1, 59 +/- 3% pred), mean H2O2 concentration in exhaled breath condensate was significantly elevated as compared with the values in 25 age-matched (mean age, 42 +/- 2 yr) normal subjects (0.87 +/- 0.01 versus 0.26 +/- 0.04 microM, p < 0.001). There was a significant negative correlation between H2O2 and FEV1 (r = -0.76, p < 0.0001). Patients treated with inhaled corticosteroids had values of H2O2 similar to those of steroid-naïve patients (0.8 +/- 0.1 versus 0.9 +/- 0.1, p > 0.05). We conclude that H2O2 is elevated in exhaled air condensate of patients with bronchiectasis and is correlated with disease severity. Measurement of H2O2 may be used as a simple noninvasive method to monitor airway inflammation and oxidative stress.

Differentiation of light-dye effects in the microcirculation

Activation of photosensitive compounds has been used in the treatment of tumors and as a technique to study various microcirculatory phenomena. This technique may be accompanied by deleterious effects which may complicate interpretations of experimental results. However, the relevant physiological mechanisms that induce toxicity and the light doses needed to produce different toxic reactions have not been well defined. In the current study, the rat cremaster muscle preparation was used with in vivo fluorescent television microscopy and subsequently with electron and light microscopy to evaluate toxic reactions of light activation of fluorescein isothiocyanate. The most sensitive photoactive reactions were macromolecular leakage and platelet activation, occurring with 120 J/cm2 activation energy. Macromolecular leakage was at least partially restricted by perivenular and pericapillary pericytes and there was no morphological damage with this light dose. Since macromolecular leakage was significantly inhibited by pretreatment with diphenhydramine or Compound 48/80, it is in part due to the release of histamine from tissue mast cells. 720 J/cm2 reduced the red blood cell column in the venules by over 50% due to platelet thrombus formation, an effect that was accentuated by pretreatment with indomethacin. This suggests an inhibitory role of prostaglandins in platelet thrombus formation. In addition, 720 J/cm2 caused endothelial and smooth muscle cell swelling and ruptures, gap formation, and leukocyte and protein accumulation in the vessel walls.

Effect of methylprednisolone on motor function and spinal cord blood flow after spinal cord compression in rats

The effect of methylprednisolone (MP) on neurologic recovery and spinal cord blood flow (SCBF) was investigated up to 4 days after a spinal cord compression injury in rats. The injury was produced at midthoracic level by applying a load of 35 g on a 2.2 x 5.0 mm compression plate for 5 min, which resulted in transient paraparesis. MP was given as a bolus dose of 30 mg/kg i.v. 60 min after injury (n = 20) and controls were given saline (n = 10). The motor performance was assessed daily as the capacity angle on the inclined plane and SCBF was measured by 14C-iodoantipyrine autoradiography on Days 1 or 4. On Day 1 the capacity angle was reduced from about 63 degrees preoperatively to 33 +/- 2 degrees (mean +/- SEM) in the control group and to 50 +/- 1 degrees in the group treated with MP (p less than 0.05). Thereafter there was a slight improvement in both groups, but the difference persisted throughout the observation period. On Day 4 both gray and white matter SCBF was better preserved in MP-treated animals than in the control group (59 +/- 4 versus 49 +/- 3 ml/min/100 g tissue for gray matter and 13.6 +/- 0.6 versus 10.7 +/- 0.8 ml/min/100 g tissue for white matter). Posttraumatic treatment with MP, thus, improved both the neurologic recovery during the first 4 days and SCBF as measured on Day 4. It is speculated that the effect of MP is at least partly exerted on the vascular bed.