Apoptosis of Wound Fibroblasts Induced by Oxidative Stress

Abstract

Irreversible lung parenchymal injury is usually healed by fibrosis, which depends on the abilities of fibroblasts to proliferate, migrate into the wound, and survive. Because the lung is frequently exposed to increased oxidative stress, which is thought to mediate apoptosis, we examined whether oxidative stress induces apoptosis in fibroblasts during wound healing. We performed an in vitro scratch wound assay where cultured fibroblast monolayers were exposed to H2O2 (10-500 microM) after artificial wounding. Apoptosis was evaluated by nuclear staining with Hoechst33342 or terminal deoxynucleotidyl transferase (TdT)-mediated nucleotide nick end-labeling (TUNEL). Intracellular oxidants were assessed with the peroxide-sensitive fluorochrome carboxydichlorodihydrofluorescein (CDCF). We found that repopulating fibroblasts at the wound margin, but not quiescent fibroblasts at the intact site, selectively underwent oxidant accumulation and apoptosis in response to H2O2 exposure. Some of the apoptotic cells had incorporated bromodeoxyuridine (BrdU), an indicator of proliferating cells. These results suggest that oxidative stress selectively induces apoptosis in fibroblasts that are stimulated to proliferate and/or migrate into the wound. Fibroblast apoptosis induced by oxidative stress during wound repopulation may be relevant to intractable wound healing.

PAR bZIP-bik is a novel transcriptional pathway that mediates oxidative stress-induced apoptosis in fibroblasts

“…30 Oxidant exposure has also been involved in the apoptotic cell death of repopulating fibroblasts during wound healing. 31 Furthermore, fibroblasts from old individuals have a reduced capacity to undergo apoptosis in response to oxidative stress compared with younger cells, 32 which may contribute to a number of age-dependent disorders. Thus, the results presented here provide a novel pathway that may help Together, this study shows a novel role for PAR bZIP proteins in the transcriptional regulation of bik, and supports that this pathway is necessary to activate the apoptotic cascade in response to oxidative stress.…”

Apoptosis in lung injury and fibrosis

“…Oxidative stress also affects fibroblast apoptosis: hydrogen peroxide causes apoptosis of fibroblasts stimulated to proliferate or migrate to the wound [56].…”

Sensitivity of myofibroblasts to H2O2‐mediated apoptosis and their antioxidant cell network

“…The induction of fibroblast apoptosis in response to oxidative stress may therefore be relevant to impaired wound healing (Takahashi et al, 2002). This study opens the door to a new therapeutic strategy and indicates that a better understanding of hypertrophic scar pathogenesis will suggest new approaches to treat pathological scarring and thus, will allow a better quality of life for these patients.…”

“…Oxidative stress is also believed to be an important mediator of apoptosis (Buttke and Sandstrom, 1994;Jacobson, 1996). Both enhanced cellular oxidant levels and depleted cellular antioxidants have been shown to induce apoptosis in various types of cells including Fb (Takahashi et al, 2002). However, it remains unknown whether oxidative stress can modulate myofibroblast apoptosis.…”