We previously showed that coincident exposure to heat shock (HS; 42°C for 2h) and TNFα synergistically induces apoptosis in mouse lung epithelium. We extended this work by analyzing HS effects on human lung epithelial responses to clinically relevant injury. Cotreatment with TNFα and HS induced little caspase-3 and PARP cleavage in human small airway epithelial cells (SAECs) and A549 and BEAS2B cells. Scratch wound closure rates almost doubled when A549 and BEAS2B cells and air-liquid interface cultures of human bronchial epithelial (NHBE) were heat-shocked immediately post-wounding. Microarray, qRT-PCR, and immunoblotting showed FGF1 to be synergistically induced by HS and wounding. Enhanced FGF1 expression in HS/wounded A549 was blocked by inhibitors of p38 MAPK (SB203580) or heat shock factor (HSF)-1 (KNK-437) and in HSF1-knockout BEAS2B cells. PCR demonstrated FGF1 to be expressed from the two most distal promoters in wounded/heat-shocked cells. Wound closure in heat-shocked A549 cells was reduced by FGF receptor-1/3 inhibition (SU-5402) or FGF1 depletion. Exogenous FGF1 accelerated A549 wound closure in the absence but not presence of HS. In the presence of exogenous FGF1, HS slowed wound closure, suggesting it increases FGF1 expression but impairs FGF1-stimulated wound closure. Frozen sections from normal and IPF lung were analyzed for FGF1 and HSP70 by immunofluorescence confocal microscopy and qRT-PCR. FGF1 and HSP70 mRNA levels were 7.5- and 5.9-fold higher in IPF than normal lung and the proteins co-localized to fibroblastic foci in IPF lung. We conclude that HS signaling may have an important impact on lung injury, healing, and fibrosis.
- Fibroblast Growth Factor-1
- Heat shock factor-1
- epithelial wound healing
- Idiopathic pulmonary fibrosis
- Heat Shock
- Copyright © 2016, American Journal of Physiology-Lung Cellular and Molecular Physiology