Pneumothorax-associated pleural eosinophilia is tumour necrosis factor-alpha-dependent and attenuated by steroids.
OBJECTIVE
The pathogenesis and the optimal treatment of eosinophilic pleural effusions are unknown. We aimed to examine whether pneumothorax-associated pleural eosinophilia in mice is dependent on tumour necrosis factor (TNF)-alpha, and whether it is affected by systemic administration of corticosteroids.


METHODS
Mice were injected intrapleurally with 0.4 mL air to create pneumothoraces. Animals were sacrificed 24 or 48 h later, and pleural lavage (PL) was performed. In the first experiment, comparisons were made between wild-type and TNF-alpha knockout mice with pneumothorax. In the second experiment, wild-type mice were injected intraperitoneally with different doses of dexamethasone (0, 0.25, 0.5 and 1 mg/kg), 5 min before and 24 h after the induction of pneumothorax.


RESULTS
After induction of a pneumothorax, TNF-alpha knockout mice had significantly fewer total number of cells (P = 0.004), mononuclear cells (P = 0.01), neutrophils (P = 0.017) and eosinophils (P = 0.002) in their PL compared with wild-type animals. TNF-alpha was detected in the PL of most of the control mice but not in TNF-alpha knockouts. Dexamethasone induced a significant, dose-dependent reduction of PL total cells (P < 0.001), eosinophils (P < 0.001), mononuclear cells (P = 0.007) and lymphocytes (P = 0.04) at 48 h, and significantly reduced the number of PL total cells (P = 0.045) and eosinophils (P = 0.005) at 24 h. Furthermore, dexamethasone prevented eosinophil infiltration of lung and pleural tissue.


CONCLUSIONS
Pneumothorax-associated pleural eosinophilia in mice is TNF-alpha-dependent and is significantly attenuated by corticosteroid treatment. In addition, both TNF-alpha deficiency and dexamethasone treatment were associated with a significant reduction of other types of inflammatory cells in PL.
Kalomenidis
Ioannis
I
Applied Biomedical Research and Training Center Marianthi Simou, Department of Critical Care and Pulmonary Services, Athens Medical School, Evangelismos Hospital, Athens, Greece. ikalom@med.uoa.gr
Moschos
Charalampos
C
Kollintza
Androniki
A
Sigala
Ioanna
I
Stathopoulos
Georgios T
GT
Papiris
Spyros A
SA
Light
Richard W
RW
Roussos
Charis
C
D000818:Animals; D003907:Dexamethasone / Q000627:therapeutic use*; D004195:Disease Models, Animal; D004802:Eosinophilia / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism*; D005938:Glucocorticoids / Q000627:therapeutic use*; D015848:Interleukin-5 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011030:Pneumothorax / Q000150:complications* / Q000378:metabolism / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
D005938:Glucocorticoids; D015848:Interleukin-5; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone