Apoptotic cell instillation after bleomycin attenuates lung injury through hepatocyte growth factor induction

Abstract

Apoptotic cell clearance by macrophages and neighbouring tissue cells induces hepatocyte growth factor (HGF) secretion. HGF plays a key role in alveolar epithelial regeneration and reconstruction after lung injury. Direct in vivo exposure to apoptotic cells enhances HGF production, resulting in attenuation of pulmonary injury.We investigated the direct effect of in vivo exposure to apoptotic cells in bleomycin-stimulated lungs (2 days old) on HGF induction. Furthermore, sequential changes of bleomycin-induced HGF production following apoptotic cell instillation related to the changes in inflammatory and fibrotic responses were assessed.At 2 h after apoptotic cell instillation into bleomycin-stimulated lungs, the levels of HGF mRNA and protein production, and apoptotic cell clearance by alveolar macrophages were enhanced. Furthermore, HGF induction persistently increased following apoptotic cell instillation up to 21 days after bleomycin treatment. Apoptotic cell instillation attenuated bleomycin-induced proinflammatory mediator production, inflammatory cell recruitment and total protein levels. Apoptotic cell instillation also induced antiapoptotic and antifibrotic effects. These antiinflammatory and antiapoptotic effects could be reversed by co-administration of HGFneutralising antibody.These findings indicate that in vivo exposure to apoptotic cells enhances transcriptional HGF production in bleomycin-stimulated lungs, resulting in attenuation of lung injury and fibrosis.

Hepatocyte Growth Factor Is Required for Mesenchymal Stromal Cell Protection Against Bleomycin-Induced Pulmonary Fibrosis

“…Evidence from the literature supports a protective role for HGF in fibrotic lung disease. Apoptotic cells have been shown to modulate bleomycin lung fibrosis through the production of HGF alone [59] or in combination with PGE 2 [60]. Notably, a recent study has identified the role for a secreted factor in MSC protection against lung fibrosis and acute lung injury using conditioned medium from amniotic membrane derived cells [61] or proinflammatory cytokineactivated MSCs [62].…”

Efferocytosis and Lung Disease

“…52 Conversely, instillation of apoptotic cells into the lungs of mice following bleomycin lung injury reduced infl ammatory cytokine production and lung fi brosis via hepatocyte growth factor-dependent mechanisms, resulting in increased survival. 53 This last fi nding suggests that autologous apoptotic cell therapy might be benefi cial in selected settings, if issues of timing and dosage could be defi ned. However, the complexity of that approach is illustrated by the fi nding that TNF-a reduced net apoptotic cell clearance from the lung and thereby increased lung infl ammation as cells progressed to secondary necrosis.…”

A STAT6 Inhibitor AS1517499 Reduces Preventive Effects of Apoptotic Cell Instillation on Bleomycin-Induced Lung Fibrosis by Suppressing PPARγ

“…Like very few other compounds this drug exerts potent anti-fibrotic effect when given during the fibrogenic phase of BLM lung [35]. Our previous studies demonstrated that anti-fibrotic effects of apoptotic cell instillation after bleomycin treatment were significant on days 14 and 21 after BLM treatment [11, 20]. In addition, anti-EMT effect of apoptotic cell instillation on primary type II alveolar epithelial cells was determined at 14 days after BLM treatment [36].…”

“…Mice were cared for and handled in accordance with the National Institute of Health (NIH) Guide for the Care and Use of Laboratory Animals. Mouse pharyngeal aspiration was used to administer the solution containing BLM (5 U/kg body weight in 30 µl) [20, 21]. Two days after BLM treatment, saline alone, or 10 × 10 6 apoptotic or viable Jurkat cells in 50 µl saline were administered intratracheally ( i.t. )…”

“…Following BAL, the cell count was determined using an electronic Coulter Counter fitted with a cell sizing analyzer (Coulter Model ZBI with a channelizer 256; Coulter Electronics, Bedfordshire, UK) [25, 26]. BAL cells were isolated and then cytospun to assess phagocytic indices by immunocytochemistry [20, 22]. The phagocytic index was calculated using the following formula: ((number of apoptotic bodies)/(200 total macrophages) x 100.…”