Reduction of bleomycin-induced sequestration of neutrophils and vascular injury in hamster lungs by nitroglycerin

Biological significance of essential fatty acids/prostanoids/lipoxygenase-derived monohydroxy fatty acids in the skin

The skin displays a highly active metabolism of polyunsaturated fatty acids (PUFA). Dietary deficiency of linoleic acid (LA), an 18-carbon (n-6) PUFA, results in characteristic scaly skin disorder and excessive epidermal water loss. Although arachidonic acid (AA), a 20-carbon (n-6) PUFA, is metabolized via cyclooxygenase pathway into predominantly prostaglandin E2 (PGE2) and PGF2alpha, the metabolism of AA via the 15-lipoxygenase (15-LOX) pathway, which is very active in skin epidermis and catalyzes the transformation of AA into predominantly 15S-hydroxyeicosatetraenoic acid (15S-HETE). Additionally, the 15-LOX also metabolizes the 18-carbon LA into 13S-hydroxyoctadecadienoic acid (13S-HODE), respectively. Interestingly, 15-LOX catalyzes the transformation of dihomo-gamma-linolenic acid (DGLA), derived from dietary gamma-linolenic acid, to 15S-hydroxyeicosatrienoic acid (15S-HETrE). These monohydroxy fatty acids are incorporated into the membrane inositol phospholipids which undergo hydrolytic cleavage to yield substituted-diacylglycerols such as 13S-HODE-DAG from 13S-HODE and 15S-HETrE-DAG from 15S-HETrE. These substituted-monohydroxy fatty acids seemingly exert anti-inflammatory/antiproliferative effects via the modulation of selective protein kinase C as well as on the upstream/down-stream nuclear MAP-kinase/AP-1/apoptotic signaling events.

Antifibrotic effect of decorin in a bleomycin hamster model of lung fibrosis

We reported previously that treatment with antibody to transforming growth factor-beta (TGF-beta) caused a marked attenuation of bleomycin (BL)-induced lung fibrosis (LF) in mice. Decorin (DC), a proteoglycan, binds TGF-beta and thereby down-regulates all of its biological activities. In the present study, we evaluated the antifibrotic potential of DC in a three-dose BL-hamster model of lung fibrosis. Hamsters were placed in the following groups: (1) saline (SA) + phosphate-buffered saline (PBS) (SA + PBS); (2) SA + DC; (3) BL + PBS; and (4) BL + DC. Under pentobarbital anesthesia, SA (4 mL/kg) or BL was instilled intratracheally in three consecutive doses (2.5, 2.0, 1.5 units/kg/4 mL) at weekly intervals. DC (1 mg/mL) or PBS was instilled intratracheally in 0.4 mL/hamster on days 3 and 5 following instillation of each dose of SA or BL. In week 4, hamsters received three doses of either DC or PBS every other day. The hamsters were killed at 30 days following the first instillation, and their lungs were appropriately processed. Lung hydroxyproline levels in SA + PBS, SA + DC, BL + PBS, and BL + DC groups were 965, 829, 1854, and 1387 microg/lung, respectively. Prolyl hydroxylase activities were 103, 289, and 193% of SA + PBS control in SA + DC, BL + PBS, and BL + DC groups, respectively. The myeloperoxidase activities in the corresponding groups were 222, 890, and 274% of control (0.525 units/lung). Intratracheal instillation of BL caused significant increases in these biochemical markers, and instillation of DC diminished these increases in the BL + DC group. DC treatment also caused a significant reduction in the infiltration of neutrophils in the bronchoalveolar lavage fluid (BALF) of hamsters in the BL + DC group. However, DC treatment had little effect on BL-induced increases in lung superoxide dismutase activity and lipid peroxidation and leakage of plasma proteins in the BALF of the BL + DC group. Hamsters in the BL + PBS group showed severe multifocal fibrosis and accumulation of mononuclear inflammatory cells and granulocytes. In contrast, hamsters in the BL + DC group showed mild multifocal septal thickening with aggregations of mononuclear inflammatory cells. Hamsters in both control groups (SA + PBS and SA + DC) showed normal lung structure. Frozen lung sections following immunohistochemical staining revealed an intense staining for EDA-fibronectin and collagen type I in the BL + PBS group as compared with all other groups. It was concluded that DC potentially offers a novel pharmacological intervention that may be useful in treating pulmonary fibrosis.

Amelioration of bleomycin-induced lung fibrosis by treatment with the platelet activating factor receptor antagonist WEB 2086 in hamsters

Therapeutic use of bleomycin, an antineoplastic drug, is complicated by the development of a dose-dependent lung toxicity leading to fibrosis. This study tested the effectiveness of a platelet activating factor (PAF) receptor antagonist, WEB 2086, against bleomycin (BLEO)-induced lung fibrosis in hamsters. The animals were assigned to four groups: (1) saline (SA) + SA, (2) WEB 2086 (WEB) + SA, (3) SA + BLEO, and (4) WEB + BLEO. Sterile isotonic saline or WEB 2086 (10 mg/kg IP) was administered daily for the duration of the study starting 2 days prior to intratracheal (IT) instillation of saline or bleomycin (2.5, 2.0, and 1.5 units/kg 5 mL-1) in three consecutive doses at weekly intervals. The animals were killed at 21 days after the last IT instillation and their lungs were processed for various studies. The lung hydroxyproline levels in SA + SA, WEB + SA, SA + BLEO, and WEB + BLEO groups were 932 +/- 31, 943 +/- 48, 1302 +/- 72, and 964 +/- 63 micrograms/lung, respectively. The lung myeloperoxidase (MPO) activity and malondialdehyde equivalent, an index of lipid peroxidation, in the corresponding groups were 10 +/- 2, 8 +/- 2, 14 +/- 3, and 5 +/- 1 units/lung and 93 +/- 7, 77 +/- 5, 102 +/- 8, and 75 +/- 6 nmol/lung, respectively. The lung prolyl hydroxylase activity in the WEB + SA, SA + BLEO, and WEB + BLEO groups was 130.1 +/- 7.7, 236.2 +/- 12.8, and 138.1 +/- 7.0% of the SA + SA control group (8.3 x 10(4) dpm/lung 30 min-1), respectively. Daily treatment with WEB 2086 caused significant (p < or = .05) reductions in the BLEO-induced increases in the lung hydroxyproline content, prolyl hydroxylase and MPO activities, lipid peroxidation, and acid phosphatase activity of the BALF supernatant. Although daily treatment with WEB 2086 reduced the bleomycin-induced increases in the BALF total and neutrophil cell counts, BALF supernatant protein, and morphometric estimates of the lesions, these parameters were not significantly different from those of the SA-BLEO group. Histopathologic studies revealed that there were no lesions of alveolar consolidation and fibrosis in the lungs of WEB + BLEO group as compared with the SA + BLEO group. The results suggest that PAF is involved in the BLEO-induced lung fibrosis and that PAF-receptor antagonist may therefore be potentially useful in the attenuation of lung fibrosis caused by bleomycin.

Effect of antibody to transforming growth factor beta on bleomycin induced accumulation of lung collagen in mice

BACKGROUND

Increased production of transforming growth factor beta (TGF-beta) seems to have an important role in the pathophysiology of bleomycin induced lung fibrosis. This is attributed to the ability of TGF-beta to stimulate infiltration of inflammatory cells and promote synthesis of connective tissue, leading to collagen deposition.

METHODS

The study was designed to evaluate the antifibrotic potential of TGF-beta antibody in mice treated with bleomycin, which is a model of lung fibrosis. Under methoxyflurane anaesthesia, each mouse received intratracheally either 50 microliters sterile isotonic saline or 0.125 units bleomycin in 50 microliters. Within five minutes after the instillation, mice received into the tail vein 100 microliters non-immune rabbit IgG, TGF-beta 2 antibody, or a combination of TGF-beta 2 and TGF-beta 1 antibodies at various dose regimens. Mice were killed 14 days after the instillation and their lungs processed for morphological and biochemical studies.

RESULTS

Administration of 250 micrograms of TGF-beta 2 antibody after instillation of bleomycin followed by 100 micrograms on day 5 and 100 micrograms on day 9 significantly reduced the bleomycin induced increases in the accumulation of lung collagen from 445.8 (42.3) micrograms/lung to 336.7 (56.6) micrograms/lung at 14 days. Similarly, the combined treatment with 250 micrograms TGF-beta 2 antibody and 250 micrograms TGF-beta 1 antibody after bleomycin instillation followed by 100 micrograms of each antibody on day 5 also caused a significant reduction in bleomycin induced increases in lung collagen accumulation and myeloperoxidase activity at 14 days.

CONCLUSIONS

These results suggest that TGF-beta has an important role in the aetiology of bleomycin induced lung fibrosis; the neutralisation of TGF-beta by systemic treatment with its antibodies offers a new mode of pharmacological intervention which may be useful in treating lung fibrosis.