Fibroblasts are key structural cells that can be damaged by cigarette smoke. Cigarette smoke contains many components capable of eliciting oxidative stress, which may induce heme oxygenase-1 (HO-1), a cytoprotective enzyme. There are no data on HO-1 expression in primary human lung fibroblasts following CSE exposure. We hypothesized human lung fibroblasts, exposed to cigarette smoke, would increase HO-1 though changes in intracellular glutathione (GSH). Primary human lung fibroblasts were exposed to cigarette smoke extract (CSE) and changes in HO-1 expression and GSH levels assessed. CSE induced a time- and dose-dependent increase in expression of HO-1, but not HO-2 or biliverdin reductase, in two different primary human lung fibroblast strains, a novel finding. This induction of HO-1 paralleled a decrease in intracellular GSH, and a sustained reduction in GSH resulted in a dramatic increase in HO-1. Treatment with the antioxidants N-acetyl-cysteine (NAC) or GSH reduced the expression of HO-1 induced by CSE. We also examined the signal transduction mechanism responsible for HO-1 induction. Nrf2 was not involved in HO-1 induction by CSE. AP-1 is a redox-sensitive transcription factor shown in other systems to regulate HO-1 expression. CSE exposure resulted in nuclear accumulation of c-Fos and c-Jun, two key AP-1 components. Reduction of c-Fos and c-Jun nuclear translocation by SP600125 attenuated the CSE-induced expression of HO-1. These data support the concept that changes in the cellular redox status brought on by cigarette smoke induces HO-1 in fibroblasts. This increase in HO-1 may help protect against cigarette smoke induced inflammation and/or cell death.