LAUSR

To the Editor: Sulfur dioxide (SO2) is one of the main air pollutants, which is formed when sulfur‐containing fuel is burned.[1] In some special situation, people may be exposed to high concentration of SO2, such as an accident of SO2 tank leakage, mine blast, smoke of gunpowder in a war, and smoke of volcanic eruption, which may be harmful to the persons who are exposed to it. Many studies have indicated that SO2 exposure increases morbidity and mortality. SO2 can not only produce a variety of adverse pulmonary effects, such as bronchitis and airway hyperresponsiveness,[2] but also have harmful effects on other systems and organs. It is associated with increased risk of acute myocardial infarction, and inhalation of SO2 can cause injury in brain including stroke. The expressions of oncogenes and tumor suppressor genes in lung and liver of rat were affected by exposure to SO2 and benzo(a)pyrene. The expressions of apoptosis‐related genes can be augmented and the apoptosis of the cells was induced in liver, lung, and brain of rats exposed to SO2. Secretory leukocyte protease inhibitor (SLPI) is a glycoprotein with a molecular weight of about 11,700.[3] SLPI is present in human mucus secretions and tissues and produced primarily in the epithelial cells lining the respiratory, digestive, and reproductive tracts.[4] Its major physiological function is to inhibit serine proteases, including cathepsin and tryptase, and to protect tissues from excessive protease digestion at the sites of inflammation in vivo.[5] It has antibacterial and antifungal properties in vitro and has been shown to prevent viral infection. SLPI inhibits the expression of inflammatory cytokines such as tumor necrosis factor (TNF)‐a, interleukin (IL)‐8, and IL‐6 via translocation from cytoplasm to nucleus and binding to nuclear factor‐kappa B binding sites.