The effect of bleomycin on lung metabolism of prostaglandin E2 in hamster

Cyclooxygenase- and lipoxygenase-derived eicosanoids in bronchoalveolar lavage fluid from patients with scleroderma lung disease: an imbalance between proinflammatory and antiinflammatory lipid mediators

OBJECTIVE

Eicosanoids play a key role in the regulation of inflammation and fibrosis. Recently we showed that levels of 5-lipoxygenase (5-LOX)-derived proinflammatory/profibrotic leukotrienes are elevated in bronchoalveolar lavage (BAL) fluid from patients with scleroderma lung disease (SLD). The present study was undertaken to investigate whether increased levels of leukotrienes are balanced by the antiinflammatory/antifibrotic cyclooxygenase (COX)- and 15-LOX-derived eicosanoids in the lungs of patients with SLD.

METHODS

Levels of 5-LOX-derived leukotriene B(4) (LTB(4)), COX-derived prostaglandin E(2) (PGE(2)), and 15-LOX-derived 15-hydroxyeicosatetraenoic acid (15-HETE) and lipoxin A(4) (LXA(4)) in BAL fluid from systemic sclerosis (SSc) patients with SLD (n = 32) and without SLD (n = 16) and from healthy individuals (n = 12) were measured by enzyme-linked immunosorbent assay.

RESULTS

Levels of LTB(4) (mean +/- SEM 248 +/- 29 pg/ml) and PGE(2) (51 +/- 10 pg/ml) in SSc patients with SLD were significantly higher compared with patients without SLD (LTB(4) 119 +/- 35 pg/ml, PGE(2) 17 +/- 3 pg/ml; P < 0.05 for both) and with healthy controls (85 +/- 12 pg/ml and 19 +/- 2 pg/ml, respectively; P < 0.05 for both). Accordingly, the mean +/- SEM PGE(2):LTB(4) ratio was similar in SSc patients with SLD (0.30 +/- 0.05), SSc patients without SLD (0.29 +/- 0.07), and controls (0.31 +/- 0.07). In contrast, levels of 15-HETE and LXA(4) in patients with SLD did not differ significantly from levels in patients without SLD or in controls. The ratio of LXA(4):LTB(4) in SLD patients (0.16 +/- 0.03) was significantly lower (P < 0.05) than that in patients without SLD (0.40 +/- 0.10) or controls (0.34 +/- 0.08).

CONCLUSION

Increased production of LTB(4) in the lungs of patients with SLD is not balanced by an up-regulation of 15-LOX-derived antiinflammatory/antifibrotic eicosanoids such as 15-HETE or LXA(4). Targeting the 5-LOX/15-LOX balance may be of practical value in the treatment of SLD.

The effect of diclofenac acid (Voltaren) on bleomycin-induced pulmonary fibrosis in hamsters

Bleomycin is an anti-neoplastic compound which produces a time- and dose-dependent pulmonary fibrosis. The mechanisms which cause this fibrosis are not known. However, the ability of bleomycin to modulate prostaglandin synthesis, degradation and circulating levels appears to be central to the fibrosis. Previous studies, which have attempt to modulate bleomycin-induced fibrosis by prevention of prostaglandin synthesis have conflicting results. Therefore, the present study was designed to determine the effects of diclofenac acid, a nonsteroidal anti-inflammatory compound, on the development of bleomycin-induced pulmonary fibrosis. Diclofenac acid pretreatment and daily injections prevented lung collagen accumulation after intratracheal bleomycin. In addition diclofenac acid treatment resulted in significantly lower lung collagen level after intratracheal bleomycin at 14 and 21 days when compared with bleomycin alone. These data indicate that diclofenac acid treatment inhibits bleomycin-induced lung fibrosis possible through the prevention of prostaglandins synthesis.

Alteration of fate of vasoactive autacoids in pulmonary circulation following monocrotaline-induced lung vascular injury in rats

1. To learn how pulmonary vascular injury alters the ability of the lung to metabolize vasoactive autacoids, lung vascular lesions were produced in rats by a single subcutaneous injection of monocrotaline (90 mg kg-1), and the blood pressure responses to angiotensin I (AI), angiotensin II (AII), bradykinin, prostaglandin E2 (PGE2) and substance P were examined. Vasoactive agents were given intravenously or intra-arterially. 2. On histological examination of the lung at 3 weeks after monocrotaline treatment, degeneration or necrotization of endothelial cells was evident. 3. The conversion of AI to AII was only slightly depressed by monocrotaline treatment. On the other hand, the depressor response to intravenously injected bradykinin was enhanced in monocrotaline-treated rats. When the rats were pretreated with indomethacin the depressor response to intravenous bradykinin was the same for both control and monocrotaline-treated groups which suggests that endogenous prostaglandins are involved in the enhancement of the response to bradykinin. 4. In monocrotaline-treated rats the depressor response to intravenous PGE2 was significantly enhanced depending on the period following the treatment, while that to the intra-arterial injection did not differ from control. 5. The data suggest that monocrotaline-induced lung injury impairs the metabolism of PGE2 during pulmonary circulation but has little effect on the conversion of AI to AII and the degradation of bradykinin in rats.

Endothelial injury caused by antineoplastic agents

The vascular lining of the blood vessels to normal organs and malignant tissues would be expected to reflect the functional demands placed upon it. These functional requirements may be accomplished by specific biochemical macromolecules, some of which are localized on the plasma membrane of the endothelium. Considerable evidence exists that toxicity to at least some normal organs caused by antineoplastic agents is heralded by endothelial damage. This endothelial damage may reflect a specific drug-endothelium interaction, the mechanism and basis of which are not yet understood. The possibility also exists that destruction of solid tumors by currently employed antitumor agents is mediated in part by local loss of essential vasculature. Selective destruction of the tumor endothelium could be a rational and novel target to which drugs could be designed.