Exposure to cigarette smoke, a major risk factor for sudden infant death syndrome: effects of cigarette smoke on inflammatory responses to viral infection and bacterial toxins

Exposure to cigarette smoke is a major risk factor for sudden infant death syndrome and also for respiratory infections in children. It has been sugge sted that toxigenic bacteria colonizing the respiratory tract might play a role in some cases of sudden infant death syndrome and nicotine has been de monstrated to enhance the lethality of bacterial toxins in a model system. Pyrogenic toxins of Staphylococcus aureus have been identified in tissues o f infants who died of sudden infant death syndrome. It has been suggested t hat some of these deaths were due to induction of inflammatory mediators by infectious agents during a period when infants are less able to control th ese responses. The aim of this study was to assess the effects of a water-s oluble cigarette smoke extract on the production of tumor necrosis factor a lpha and nitric oxide from human monocytes in response to staphylococcal to xic shock syndrome toxin 1 or infection of the monocytes with respiratory s yncytial virus. Cell culture supernatants were examined by a bioassay using mouse fibroblasts (L-929 cell line) for tumor necrosis factor alpha activi ty and by a spectrophotometric method for nitrite. Compared with monocytes incubated with medium only, monocytes incubated with any of the factors or their combinations tested in the study released higher levels of tumor necr osis factor alpha and lower levels of nitric oxide. Incubation with cigaret te smoke extract increased tumor necrosis factor tx from respiratory syncyt ial virus-infected cells while it decreased tumor necrosis factor alpha fro m cells incubated with toxic shock syndrome toxin. Incubation with cigarett e smoke extract decreased the nitric oxide production from respiratory sync ytial virus-infected cells while it increased the nitric oxide production f rom cells incubated with toxic shock syndrome toxin. Monocytes from a minor ity of individuals demonstrated extreme tumor necrosis factor alpha respons es and/or very high or very low nitric oxide. The proportion of samples in which extreme responses with a very high tumor necrosis factor alpha and ve ry low nitric oxide were detected was increased in the presence of the thre e agents to 20% compared with 0% observed with toxic shock syndrome toxin 1 or 4% observed with cigarette smoke extract or respiratory syncytial virus . (C) 1999 Federation of European Microbiological Societies. Published by E lsevier Science B.V, All rights reserved.