Effect of cigarette smoking on haem-oxygenase expression in alveolar macrophages.

We investigated the effect of chronic cigarette smoking on the expression of haem-oxygenase (HO)-1 and HO-2. Normal subjects and asymptomatic young current smokers with normal lung function tests underwent bronchoalveolar lavage for recovery of macrophages. Reverse transcription/polymerase chain reaction (RT-PCR) analysis showed no significant difference in HO-1 and HO-2 mRNA expression between the two groups. On the other hand, Western blot analysis showed a significant (P<0.05) reduction of HO-2 protein, but not of HO-1, in alveolar macrophages from smokers compared to normal. There was no significant differences by immunocytochemistry for HO-1 and HO-2 expression between the groups. We concluded that HO-2 expression is reduced in alveolar macrophages of smokers, possibly due to the oxidative stress of cigarette smoke. This may in turn lead to reduced protection against further oxidative insults.