Human eosinophils regulate human lung- and skin-derived fibroblast propertiesin vitro: A role for transforming growth factor β (TGF-β)

Abstract

Eosinophils have been associated with fibrosis. To investigate their direct role in fibrosis, human peripheral blood eosinophil sonicate was added to human lung or dermal fibroblasts, and proliferation ([ 3 H]thymidine) and collagen synthesis ([ 3 H]proline) were evaluated. Proliferation was enhanced significantly in the monolayers in a dosedependent manner. The activity of the eosinophil fibrogenic factor(s) remained unaltered when heated (56°C, 30 min). Supernatants of cultured eosinophils (20 min or 18 hr) also enhanced lung fibroblast proliferation, indicating that the preformed mitogenic factor(s) can be released both promptly and with a long kinetic. Eosinophils significantly decreased collagen production in lung fibroblasts while increasing it in dermal fibroblasts. However, eosinophils containing matrix metalloproteinase 9 (zymography) in latent form and tissue inhibitors of metalloproteinases 1 and 2 (reverse zymography) did not inf luence either fibroblast matrix metalloproteinases or tissue inhibitors of metalloproteinases. Eosinophil sonicate added to skin and lung fibroblasts in tridimensional collagen lattices significantly enhanced lattice contraction. Transforming growth factor ␤ (TGF-␤) is a major fibrogenic cytokine produced by eosinophils. Therefore, to assess its role, eosinophil sonicate was preincubated with anti-TGF-␤ neutralizing antibodies. This treatment partially inhibited proliferation of lung and collagen synthesis of dermal fibroblasts and suppressed the stimulation of lattice contraction, indicating the fibrogenic role of eosinophil-associated TGF-␤. In conclusion, we have shown that eosinophils act as direct modulatory cells in fibroblast proliferation, collagen synthesis, and lattice contraction, in part, through TGF-␤. These data corroborate the importance of eosinophils in skin and lung fibrosis.

Marked Airway Eosinophilia Prevents Development of Airway Hyper-responsiveness During an Allergic Response in IL-5 Transgenic Mice

“…Indeed, in humans, inhalation of rIL-5 in patients with asthma increased airway eosinophilia, sputum eosinophil cationic protein levels, and AHR (45), suggesting that IL-5 alone is sufficient to activate human eosinophils and to induce physiological changes in the airways. On the other hand, like human eosinophils (39,40), mouse eosinophils produced TGF-␤1 and retained their ability to up-regulate TGF-␤1 production in response to IL-5 and IL-3 (Fig. 4A).…”

“…In human asthma, activated eosinophils are a major source of TGF-␤1 by in situ hybridization (19) and immunohistochemistry (20). Isolated human eosinophils produce both TGF-␤1 protein (39) and TGF-␤1 bioactivity (40). Eosinophil-derived TGF-␤1 activity may not be limited to inhibiting AHR, but it may extend to immunoregulation, wound healing, tissue repair, and fibrosis.…”

Alpha-Smooth Muscle Actin Expression Upregulates Fibroblast Contractile Activity

“…Among cytokines implicated in myofibroblast differentiation, TGF␤ has been proven to directly induce ␣-SMA expression in vivo and in vitro (Desmoulière et al, 1993;Rønnov-Jessen and Petersen, 1993). A series of studies with the use of free-floating collagen gels reported TGF␤-induced fibroblast contraction, but did not consider the expression of ␣-SMA (Montesano and Orci, 1988;Finesmith et al, 1990;Tingstrom et al, 1992;Pena et al, 1994;Riikonen et al, 1995;Levi-Schaffer et al, 1999) with two exceptions (Arora and McCulloch, 1994;Kurosaka, 1995;2154). However, it was shown recently that the mechanisms of mechanically unloaded free-floating gel reduction considerably differ from stressed gel contraction (for review see Grinnell, 2000).…”

Eosinophils: a new player in coronary atherosclerotic disease

“…20 Some of the eosinophil mediators, such as transforming growth factor-beta, IL-4, IL-6, tumor necrosis factor-alpha, ECP and major basic protein can be fibrogenic. 21 Interestingly, of these factors, transforming growth factor-beta has been reported to enhance in vitro calcification of vascular cells. 22 Finally, eosinophils synthesize and release bioactive mediators, such as leukotriene C4, a potent stimulant of vasoactivity and smooth muscle contraction, and they can induce the release of a number of vasoactive substances, including histamine, prostaglandin D2 and leukotrienes C4 and D4, from mast cells and basophils.…”