Blockage of vascular endothelial growth factor (VEGF) reduces experimental pleurodesis

[Analysis of endothelial dysfunction in the context of pleural effusions of various origins using skin thermometry]

OBJECTIVE

To analyze the mechanisms and severity of endothelial dysfunction in patients with pleural effusion of various origins using skin thermometry.

MATERIAL AND METHODS

We studied microcirculation in 135 patients with pleural effusions of various origins. Local skin thermometry and computer wavelet analysis were performed in 3-5 days after thoracoscopy with pleural biopsy using Microtest-100WF device with a temperature measuring resolution of 0.001°C. We estimated endothelial, myogenic and neurogenic indices using spectral analysis of skin temperature fluctuations in a range 0.0095-2 Hz. The control group comprised 40 healthy participants aged 23-36 years.

RESULTS

Three groups of patients were distinguished depending on the cause of effusion: malignant pleural effusions (n=65, 48.1%); inflammatory pleural effusions (para-pneumonic, post-traumatic, pancreatogenic, tuberculous) (n=58, 43%); transudates (hepatogenic, cardiogenic, and nephrogenic) (n=12, 8.9%). There were no significant differences in vascular tone in response to local heating of the second finger of the hand up to 40°C. Measurements were carried out within 10 min in all groups. Patients with diabetes mellitus and cardiovascular diseases (n=48, 35.6%) had significant decrease of thermal vasodilation index in endothelial range up to 2.93±1.77, in the control group - up to 4.21±2.40 (p=0.041).

CONCLUSION

Endothelial dysfunction is a universal non-specific aspect in pathogenesis of various diseases. This process is essential in pleural effusion. Local thermometry and computer wavelet analysis revealed no significant differences between patients with malignant, inflammatory and transudative pleural effusions. Pleural effusions in the context of cardiovascular pathology and/or diabetes mellitus occur due to impaired vasodilatation mechanisms in endothelial range.

The anti-adhesive effect of anti-VEGF agents in experimental models: A systematic review

Adhesions constitute a major problem in abdominal-pelvic and thoracic surgery with significant impact in the postoperative quality of life and healthcare services utilization. Adhesiogenesis is the result of increased fibrin formation, impaired fibrinolysis, angiogenesis, and fibrosis. Despite the recent advancements, the ideal anti-adhesive agent remains to be determined. To this end, we performed a comprehensive literature search in PubMed, EMBASE, and Scopus databases to identify studies investigating the antiadhesive role of anti-VEGF agents in peritoneal, pleural, and pericardial experimental adhesion models. Fifteen studies were eligible for inclusion with a total population of 602 animals (334 rats, 180 rabbits, and 88 mice). The majority of included studies (11/15) used bevacizumab, while three studies used other anti-VEGF antibodies and one study used an anti-VEGFR-antibody. A rat model was used in nine studies, while rabbit (n = 3) or mouse (n = 3) models were used less frequently. Eleven studies used peritoneal models, three studies used pleural models, and one study used a pericardial model. The scales (n = 12) and interval (Range: 1-42 days) used for the evaluation of adhesions varied between the studies. All studies demonstrated a significant decrease in adhesion scores between the anti-VEGF and control groups up to 42 days postprocedure. VEGF blockade resulted in decreased fibrosis in four out of five studies that used peritoneal models, while the effect on pleural models depended on the pleurodesis agent and was significant between 7 and 28 days. The effect of anti-VEGF agents on anastomosis integrity depends on the dose and the model that is used (inconclusive results).Current data support the anti-adhesive role of Anti-VEGF agents in all three serosal surfaces up to 6 weeks postprocedure. Further studies are needed to confirm the anti-adhesive role of anti-VEGF agents in pleural and pericardial adhesion experimental models and investigate any effect on anastomosis integrity in peritoneal models.

Bevacizumab plus chemotherapy in nonsquamous non-small cell lung cancer patients with malignant pleural effusion uncontrolled by tube drainage or pleurodesis: A phase II study North East Japan Study group trial NEJ013B

Background

Pleurodesis is the standard of care for non‐small cell lung cancer (NSCLC) patients with symptomatic malignant pleural effusion (MPE). However, there is no standard management for MPE uncontrolled by pleurodesis. Most patients with unsuccessful MPE control are unable to receive effective chemotherapy. Vascular endothelial growth factor (VEGF) plays an important role in the pathogenesis of MPE. This multicenter, phase II study investigated the effects of bevacizumab plus chemotherapy in nonsquamous NSCLC patients with unsuccessful management of MPE.

Methods

Nonsquamous NSCLC patients with MPE following unsuccessful tube drainage or pleurodesis received bevacizumab (15 mg/kg) plus chemotherapy every three weeks. The primary endpoint was pleural effusion control rate (PECR), defined as the percentage of patients without reaccumulation of MPE at eight weeks. Secondary endpoints included pleural progression‐free survival (PPFS), safety, and quality of life (QoL).

Results

A total of 20 patients (median age: 69 years; 14 males; 20 adenocarcinomas; six epidermal growth factor receptor mutations) were enrolled in nine centers. The PECR was 80% and the primary end point was met. The PPFS and the overall survival (OS) were 16.6 months and 19.6 months, respectively. Patients with high levels of VEGF in the MPE had shorter PPFS (P = 0.010) and OS (P = 0.002). Toxicities of grade ≥ 3 included neutropenia (50%), thrombocytopenia (10%), proteinuria (10%), and hypertension (2%). The cognitive QoL score improved after treatment.

Conclusions

Bevacizumab plus chemotherapy is highly effective with acceptable toxicities in nonsquamous NSCLC patients with uncontrolled MPE, and should be considered as a standard therapy in this setting.

Key points

Significant findings of the study

Bevacizumab plus chemotherapy is highly effective with acceptable toxicities in nonsquamous NSCLC patients with uncontrolled MPE.

What this study adds

Bevacizumab plus chemotherapy should be considered as a standard treatment option for patients with uncontrolled MPE.

Clinical trial registration

UMIN000006868 was a phase II study of efficacy of bevacizumab plus chemotherapy for the management of malignant pleural effusion (MPE) in nonsquamous non‐small cell lung cancer patients with MPE unsuccessfully controlled by tube drainage or pleurodesis (North East Japan Study Group Trial NEJ‐013B) (http://umin.sc.jp/ctr/).

Chemical pleurodesis - a review of mechanisms involved in pleural space obliteration

Chemical pleurodesis is a therapeutic procedure applied to create the symphysis between the parietal and visceral pleura by intrapleural administration of various chemical agents (e.g. talk, tetracycline, iodopovidone, etc.). The two major clinical conditions treated with chemical pleurodesis are recurrent pleural effusion (PE) and recurrent spontaneous pneumothorax. Although the history of chemical pleurodesis began over a century ago, detailed data on the mechanisms of action of sclerosing agents are highly incomplete. The following article aims to present the state of knowledge on this subject.It is believed that mesothelial cells are the main structural axis of pleurodesis. In response to sclerosing agents they secrete a variety of mediators including chemokines such as interleukin 8 (IL-8) and monocyte chemoattractant protein (MCP-1), as well as growth factors - vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF) and transforming growth factor- β (TGF-β). Numerous data suggest that intact mesothelial cells and the above cytokines play a crucial role in the initiation and maintenance of different pathways of pleural inflammation and pleural space obliteration.It seems that the process of pleurodesis is largely nonspecific to the sclerosant and involves the same ultimate pathways including activation of pleural cells, coagulation cascade, fibrin chain formation, fibroblast proliferation and production of collagen and extracellular matrix components. Of these processes, the coagulation cascade with decreased fibrinolytic activity and increased fibrinogenesis probably plays a pivotal role, at least during the early response to sclerosant administration.A better understanding of various pathways involved in pleurodesis may be a prerequisite for more effective and safe use of various sclerosants and for the development of new, perhaps more personalized therapeutic approaches.

Decrease in VEGF-Induced Pericardial Adhesion Formation Using Bevacizumab After Surgery

OBJECTIVES

Some degrees of postoperative cardiac adhesions occur in response to the first cardiac surgery in patients that may limit surgeons for subsequent operations and increase the risk of heart injury. In this article, we established a model of postoperative pericardial adhesions, and because vascular endothelial growth factor (VEGF) seems to initiate adhesion formation through inflammatory responses, we used an anti-VEGF antibody, that is, bevacizumab, to examine its effects on postoperative adhesion formation.

METHODS

Twenty Wistar rats were divided in 2 groups: control and bevacizumab. After chest opening, pericardial sac was opened and the heart was fully exposed. In the bevacizumab group, bevacizumab (2.5 mg/kg) was applied locally on the heart and then the chest was closed. The control group received saline solution as placebo. After 42 days, high-sensitivity C-reactive protein in peripheral blood was measured, and re-sternotomy was performed to measure severity of pericardial adhesions. Then, the hearts were collected from all rats to evaluate percentage of CD-31-positive cells (as a marker of angiogenesis) using immunohistochemical staining.

RESULTS

When the bevacizumab group was compared with the control group, we found that the mean score of adhesion (0.89 ± 0.38 vs 2.56 ± 0.41) and CD-31 expression (27.45 ± 3.75% vs 56.26 ± 1.98%) was decreased significantly after bevacizumab administration. However, we did not find any difference in high-sensitivity C-reactive protein levels of control and bevacizumab animals.

CONCLUSION

In the current study, bevacizumab administration could effectively reduce adhesion formation after first sternotomy by preventing VEGF-induced angiogenesis through CD-31 downregulation.

Role of bevacizumab in the management of the patient with malignant pleural effusion: more questions than answers

INTRODUCTION

Malignant pleural effusion (MPE) is a feature of metastatic cancer associated with significant morbidity and cost. The typical management of MPE is systemic chemotherapy and mechanical intervention. Vascular endothelial growth factor (VEGF), an inducer of vascular permeability, has been shown to mediate fluid formation. Therefore, bevacizumab, an inhibitor of VEGF, offers theoretical promise for abolishing fluid formation in MPE. Areas covered: This review begins with a summary of VEGF physiology and evidence of its role in MPE pathogenesis. This is followed by an overview of bevacizumab and major trials that put it on the map of non-small cell lung cancer (NSCLC). The majority of the article is devoted to a review of the current evidence base for the use of bevacizumab for MPE control in metastatic pleural malignancy. The review concludes with considerations of patient selection and toxicity. Expert commentary: Evidence in support of bevacizumab administration for MPE management remains flawed. Small studies suggest efficacy of both intravenous and intrapleural routes, but their design raises bias concerns. Bevacizumab appears to be safe in properly selected cases. The future of MPE management may de-emphasize VEGF inhibition in favor of precise molecular therapeutics that could address the root cause of tumorigenesis.

Release of growth factors after mechanical and chemical pleurodesis for treatment of malignant pleural effusion: a randomized control study

Background

Growth factors are key inducers of fibrosis but can also mediate inflammatory responses resulting in increasing pleural effusion and acute respiratory distress syndrome. The primary aim of the study was to analyse growth factors release after performing chemical and mechanical pleurodesis in the first 48 hours at the patients with malignant pleural effusion. The secondary endpoints were to evaluate the effectiveness of the both pleurodeses, symptoms release and the quality of life of patients after the treatment.

Patients and methods.

A prospective randomized study included 36 consecutive female patients with breast carcinoma and malignant pleural effusion in an intention-to-treat analysis. We treated 18 patients by means of thoracoscopic mechanical pleurodesis and 18 patients by chemical pleurodesis with talcum applied over a chest tube. We gathered the pleural fluid and serum samples in the following 48 hours under a dedicated protocol and tested them for growth factors levels. A quality of life and visual analogue pain score surveys were also performed.

Results

Median measured serum vascular endothelial growth factor (VEGF) level after chemical pleurodesis was 930.68 pg/ml (95% CI: 388.22–4656.65) and after mechanical pleurodesis 808.54 pg/ml. (95% CI: 463.20-1235.13) (p = 0.103). Median pleural levels of transforming growth factor (TGF) β1 were higher after performing mechanical pleurodesis (4814.00 pg/ml [95% CI: 2726.51–7292.94]) when compared to those after performing chemical pleurodesis (1976.50 pg/ml [95% CI: 1659.82–5136.26]) (p = 0.078). We observed similar results for fibroblast growth factor (FGF) β; the serum level was higher after mechanical pleurodesis (30.45 pg/ml [95% CI: 20.40–59.42]), compared to those after chemical pleurodesis (13.39 pg/ml [95% CI: 5.04 – 74.60]) (p = 0.076). Mechanical pleurodesis was equally effective as chemical pleurodesis in terms of hospital stay, pleural effusion re-accumulation, requiring of additional thoracentesis, median overall survival, but, it shortened the mean thoracic drainage duration (p = 0.030) and resulted in a higher symptoms release and in a better quality of life (p = 0.047).

Conclusions

We recorded an increase in serum VEGF levels after chemical pleurodesis, however on the contrary, an increase in the pleural fluid level of TGFβ1 and FGFβ] after mechanical pleurodesis with respect to compared group. Although the differences did not reach statistical significance, VEGF, TGFβ1 and FGFβ remain the most interesting parameters for future research. Considering the mechanisms of growth factors action, we conclude that in our study group mechanical pleurodesis might be more efficient in terms of growth factors release, thoracic drainage duration and resulted in a higher symptoms release and in a better quality of life than chemical pleurodesis.

A modified experimental model of malignant pleural disease induced by lung Lewis carcinoma (LLC) cells

Background

Malignant pleural effusion resulting mainly from pleural metastases of lung adenocarcinoma has clinical relevance, being a sign of poor prognosis and low life expectancy. Experimental models can mimic the human condition, contributing to advances in current understanding of the mechanisms patients’ pleural fluid accumulation and possible therapeutic strategies. The objective of this study is to evaluate the role of different concentrations of Lewis lung carcinoma cells (LLC cells) at the time of induction of experimental MPE and the main effects on survival of animals.

Methods

C57BL/6 mice received intrapleural injection of 0.1, 0.5 or 1.5 × 10⁵ LLC cells and survival curve, biochemical and pathological analyses of pleural fluid and tissue were analyzed.

Results

Evaluation of weight loss, mobility and survival showed that animals that received 0.5 × 10⁵ cells maintained more stable condition up to day 14 and a gain of 6 days survival over mice that received the highest concentration.

Conclusion

This study may allow a better understanding the mechanisms involved in the development of malignant pleural effusion and it may be promising in evaluating therapy to avoid recurrence, as the best time to indicate pleurodesis or target therapies.

VEGF correlates with inflammation and fibrosis in tuberculous pleural effusion

Objective. To investigate the relationship among angiogenic cytokines, inflammatory markers, and fibrinolytic activity in tuberculous pleural effusion (TBPE) and their clinical importance. Methods. Forty-two patients diagnosed with TBPE were studied. Based on chest ultrasonography, there were 26 loculated and 16 nonloculated TBPE patients. The effusion size radiological scores and effusion vascular endothelial growth factor (VEGF), interleukin- (IL-) 8, plasminogen activator inhibitor type-1 (PAI-1), and tissue type plasminogen activator (tPA) were measured. Treatment outcome and pleural fibrosis, defined as radiological residual pleural thickening (RPT), were assessed at 6-month follow-up. Results. The effusion size and effusion lactate dehydrogenase (LDH), VEGF, IL-8, PAI-1, and PAI-1/tPA ratio were significantly higher, while effusion glucose, pH value, and tPA were significantly lower, in loculated than in nonloculated TBPE. VEGF and IL-8 correlated positively with LDH and PAI-1/tPA ratio and negatively with tPA in both loculated and nonloculated TBPE. Patients with higher VEGF or greater effusion size were prone to develop RPT (n = 14; VEGF, odds ratio 1.28, P = 0.01; effusion size, odds ratio 1.01, P = 0.02), and VEGF was an independent predictor of RPT in TBPE (receiver operating characteristic curve AUC = 0.985, P < 0.001). Conclusions. Effusion VEGF correlates with pleural inflammation and fibrosis and may be targeted for adjunct therapy for TBPE.

Lung cancer coexisting with ipsilateral pleural effusion

SUMMARY 

Invasion beyond the elastic layer of the visceral pleura and/or diffuse pleural metastatic spread affects negatively survival in lung cancer. Presence of pleural effusion is also associated with poor prognosis, and image techniques can be of great help for diagnosis. When pleural fluid cytology is negative, thoracoscopy is advisable before attempting tumor resection, in order to detect unsuspected pleural metastases. If widespread pleural malignancy is confirmed, chemical pleurodesis using graded talc (with particles larger than 20 µm in diameter) is the best option, unless the lung is unable to re-expand. In this case, or when a previous pleurodesis has failed, or there is a short life expectancy, placement of a indwelling pleural catheter is the treatment of choice.

The role of vascular endothelial growth factor in the pathogenesis, diagnosis and treatment of malignant pleural effusion

Malignant pleural effusions (MPEs) are a significant source of cancer-related morbidity. Over 150,000 patients in the United States suffer from breathlessness and diminished quality of life due to MPE each year. Current management strategies are of mostly palliative value and focus on symptom control; they do not address the pathobiology of the effusion, nor do they improve survival. Further elucidation of the pathophysiological mechanisms, coupled with the development of novel treatments such as intrapleural chemotherapeutics targeting this process, has the potential to greatly improve the efficacy of our current management options. Vascular endothelial growth factor-A (VEGF-A) has been implicated as a critical cytokine in the formation of malignant pleural effusions. Elevated levels of VEGF produced by tumor cells, mesothelial cells, and infiltrating immune cells result in increased vascular permeability, cancer cell transmigration, and angiogenesis. Therefore antiangiogenic therapies such as Bevacizumab, a monoclonal antibody targeting VEGF-A, may have a potential role in the management of malignant pleural effusions. Herein we review the pathogenesis and potential treatment strategies of malignant pleural effusions, with a focus on angiogenesis and antiangiogenic therapeutics.

Effectiveness and safety of iodopovidone in an experimental pleurodesis model

OBJECTIVES

Chemical pleurodesis is an important therapeutic tool to control recurrent malignant pleural effusion. Among the various sclerosing agents, iodopovidone is considered effective and safe. However, in a recent study, ocular changes were described after iodopovidone was used in recurrent pneumothorax. The aim of the study was to evaluate the efficacy and morbidity of iodopovidone pleurodesis in an experimental model.

METHODS

New Zealand rabbits were submitted to intrapleural injection of iodopovidone at concentrations of 2%, 4% and 10%. Biochemical (lactic dehydrogenase, proteins, triiodothyronine, free thyroxine, urea and creatinine) and immunological (Interleukin-8 [IL-8], VEGF and TGFβ) parameters were measured in the pleural fluid and blood. After 1, 3, 7, 14 and 28 days, groups of animals were euthanized, and macro- (pleura) and microscopic (pleura and retina) analyses were performed.

RESULTS

An early pleural inflammatory response with low systemic repercussion was observed without corresponding changes in thyroid or renal function. The higher concentrations (4% and 10%) correlated with greater initial exudation, and maximum pleural thickening was observed after 28 days. No changes were observed in the retinal pigment epithelium of the rabbits.

CONCLUSION

Iodopovidone is considered to be an effective and safe sclerosing agent in this animal model. However, its efficacy, tolerance and safety in humans should be further evaluated.

Intrapleural combination therapy with bevacizumab and cisplatin for non-small cell lung cancer‑mediated malignant pleural effusion

Malignant pleural effusion (MPE) is a common complication of advanced non-small cell lung cancer (NSCLC). Bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor (VEGF), has been shown to be efficient in suppressing the accumulation of pleural fluid. However, whether intrapleural delivery of bevacizumab can be used to treat MPE remains unknown. The aim of the present study was to evaluate the efficacy and safety of combined intrapleural therapy with bevacizumab and cisplatin, an antineoplastic agent, in controlling MPE. A total of 72 NSCLC study subjects with MPE were randomly assigned to one of two groups. The first group received intrapleural bevacizumab (300 mg) with cisplatin (30 mg) therapy and the second group received intrapleural cisplatin (30 mg) therapy alone. Pleural fluid was collected from both groups prior to and following treatment. The levels of VEGF and carcinoembryonic antigen (CEA) in the pleural fluid were determined by ELISA. In 70 evaluable study subjects, the curative efficacy in the bevacizumab group was significantly higher than that found in the cisplatin group (83.33 vs. 50.00%, respectively; p<0.05). Therapy with combined bevacizumab plus cisplatin significantly reduced VEGF levels in the pleural fluid (p<0.01). In the bevacizumab group, the levels of VEGF in the pleural fluid were significantly lower compared to those of the cisplatin group after treatment, which showed greater efficacy (p<0.01). In addition, combination therapy showed greater efficacy in the patients with high levels of VEGF expression (p<0.01). There was no significant difference in grade III/IV adverse events between the two groups. All procedures were well tolerated by the patients. Combined intrapleural therapy with bevacizumab and cisplatin was effective and safe in managing NSCLC-mediated MPE. We propose that VEGF expression levels in MPE could serve as a prognostic marker for bevacizumab therapy.

Bevacizumab diminishes experimental autoimmune encephalomyelitis by inhibiting spinal cord angiogenesis and reducing peripheral T-cell responses

Angiogenesis in the animal model of multiple sclerosis experimental autoimmune encephalomyelitis (EAE) is regulated by vascular endothelial growth factor (VEGF) and angiopoietin-2. We determined whether VEGF blockade with the anti-VEGF monoclonal antibody bevacizumab could inhibit angiogenesis and affect peripheral pathogenic immune responses in EAE. Mice treated with bevacizumab from the time of onset of clinical signs showed reduced clinical and pathologic scores. Bevacizumab suppressed angiogenesis and reduced angiopoietin-2 expression at Day 21 but had no effect on VEGF upregulation at Day 14. Messenger RNA levels for the angiogenesis-related protein CD105 were increased at Day 14. Bevacizumab reduced vascular permeability in the spinal cord at Day 14 and Day 21. In peripheral lymph nodes, it induced retention of CD4-positive T cells and inhibited T-cell proliferation. It also reduced mononuclear cell infiltration into spinal cord and the relative proportion of T cells. Isolated lymphoid cells showed reduced secretion of the T-helper 17 (Th-17) cell cytokine interleukin 17 and the Th-1 cytokine interferon-γ. When bevacizumab was added to naive T cells or to antigen-stimulated T cells from mice with untreated EAE in vitro, it had no effect on proliferation or the secretion of interleukin 17 or interferon-γ. These data indicate that bevacizumab ameliorates vascular and T-cell responses during EAE, but its effects on T cells may be indirect, possibly by suppressing angiogenesis.

Clinical importance of angiogenic cytokines, fibrinolytic activity and effusion size in parapneumonic effusions

OBJECTIVE

To investigate the relationship among angiogenic cytokines, fibrinolytic activity and effusion size in parapneumonic effusion (PPE) and their clinical importance.

METHODS

From January 2008 through December 2010, 26 uncomplicated (UPPE) and 38 complicated (CPPE) PPE were studied. Based on chest ultrasonography, there were non-loculated in 30, uni-loculated in 12, and multi-loculated effusions in 22 patients. The effusion size radiological scores, and effusion vascular endothelial growth factor (VEGF), interleukin (IL)-8, plasminogen activator inhibitor type-1 (PAI-1) and tissue type plasminogen activator (tPA) were measured on admission. Treatment outcome and pleural fibrosis, defined as radiological residual pleural thickening (RPT), were assessed at 6-month follow-up.

RESULTS

The effusion size and effusion VEGF, IL-8 and PAI-1/tPA ratio were significantly higher in CPPE than in UPPE, and significantly higher in multi-loculated PPE than in non-locualted and uni-loculated PPE, respectively. VEGF (cutoff value 1975 pg/ml) and IL-8 (cutoff value 1937 pg/ml) seemed best to discriminate between UPPE and CPPE. VEGF, IL-8 and effusion size correlated positively with PAI-1/tPA ratio in both UPPE and CPPE. Moreover, the level of VEGF, but not IL-8, correlated positively with effusion size in all patients (r = 0.79, p<0.001) and in UPPE (r = 0.64, p<0.001) and CPPE (r = 0.71, p<0.001) groups. The patients with higher VEGF or greater effusion were prone to have medical treatment failure (n = 10; VEGF, odds ratio 1.01, p = 0.02; effusion size, odds ratio 1.26, p = 0.01). Additionally, ten patients with RPT had larger effusion size and higher levels of VEGF and PAI-1/tPA ratio than did those without.

CONCLUSIONS

In PPE, VEGF and IL-8 levels are valuable to identify CPPE, and higher VEGF level or larger effusion is associated with decreased fibrinolytic activity, development of pleural loculation and fibrosis, and higher risk of medical treatment failure.

Monoclonal antibodies anti-TGFβ1 and anti-VEGF inhibit the experimental pleurodesis induced by silver nitrate

BACKGROUND

The mechanisms underlying pleural inflammation and pleurodesis are poorly understood. We hypothesized that the cytokines transforming growth factor β (TGFβ1) and vascular endothelial growth factor (VEGF) play a major role in pleurodesis after intrapleural silver nitrate (SN) injection.

METHOD

Forty rabbits received intrapleurally 0.5% SN alone or 0.5% SN + anti-TGFβ1, anti-IL-8, or anti-VEGF. After 28 days, the animals were euthanized and macroscopic pleural adhesions, microscopic pleural fibrosis, and collagen deposition were analyzed for characterization of the degree of pleurodesis (scores 0-4).

RESULTS

Scores of pleural adhesions, pleural fibrosis, total collagen, and thin collagen fibers deposition after 28 days were significantly lower for 0.5% SN + anti-TGFβ1 and 0.5% SN + anti-VEGF. Significant correlations were found between macroscopic adhesion and microscopic pleural fibrosis with total collagen and thin collagen fibers.

CONCLUSIONS

We conclude that both TGFβ1 and VEGF, but not IL-8, mediate the pleural inflammatory response and pleurodesis induced by SN.

Role of talc modulation on cytokine activation in cancer patients undergoing pleurodesis

We investigate the mechanism of talc pleurodesis (TP) in 20 patients with recurrent malignant pleural effusion and 10 patients with nonmalignant pleural effusions. We measured IL-8 levels before and 6 h after TP and find a significant threefold increase (2.26 ng/mL ± 0.7 to 6.5 ng/mL 0.1), which explains the recruitment of inflammatory cells in these patients. We hypothesize that TP is enable by stimulating the mesothelial cells (MS) to secrete FGF. A significant tenfold increase in FGF-b (0.05 ng/mL ± 0.02 to 0.44 ng/mL 0.6) was seen 24 h after talc instillation (P < 0.04). In order to examine whether FGF-b is secreted by MS cells, MS recovered from CHF patients with recurrent pleural effusions were cultured for 48 h in the presence or absence of increasing concentrations of talc (from 100 ng/mL to 1 mg/mL). They produced significant levels of FGF-b in a dose dependent manner (P < 0.005). We hypothesized that a successful pleurodesis involves an early enhanced recruitment of inflammatory cells through a rise of IL-8 followed by enrollment of fibroblasts from the submesothelial space through increased mesothelial FGF-b production.