Depression of stimulated arachidonate metabolism and superoxide production in rat alveolar macrophages following in vivo exposure to 0.5 ppm NO2

Exercise-Mediated Protection against Air Pollution-Induced Immune Damage: Mechanisms, Challenges, and Future Directions

Air pollution, a serious risk factor for human health, can lead to immune damage and various diseases. Long-term exposure to air pollutants can trigger oxidative stress and inflammatory responses (the main sources of immune impairment) in the body. Exercise has been shown to modulate anti-inflammatory and antioxidant statuses, enhance immune cell activity, as well as protect against immune damage caused by air pollution. However, the underlying mechanisms involved in the protective effects of exercise on pollutant-induced damage and the safe threshold for exercise in polluted environments remain elusive. In contrast to the extensive research on the pathogenesis of air pollution and the preventive role of exercise in enhancing fitness, investigations into exercise resistance to injury caused by air pollution are still in their infancy. In this review, we analyze evidence from humans, animals, and cell experiments on the combined effects of exercise and air pollution on immune health outcomes, with an emphasis on oxidative stress, inflammatory responses, and immune cells. We also propose possible mechanisms and directions for future research on exercise resistance to pollutant-induced damage in the body. Furthermore, we suggest strengthening epidemiological studies at different population levels and investigations on immune cells to guide how to determine the safety thresholds for exercise in polluted environments.

Outdoor Air Pollution: Nitrogen Dioxide, Sulfur Dioxide, and Carbon Monoxide Health Effects

Nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide are important ambient air pollutants. High-intensity, confined space exposure to NO2 has caused catastrophic injury to humans, including death. Ambient NO2 exposure may increase the risk of respiratory tract infections through the pollutant's interaction with the immune system. Sulfur dioxide (SO2) contributes to respiratory symptoms in both healthy patients and those with underlying pulmonary disease. Controlled human exposure studies have demonstrated that experimental SO2 exposure causes changes in airway physiology, including increased airways resistance. Both acute and chronic exposure to carbon monoxide are associated with increased risk for adverse cardiopulmonary events, including death. However, studies have not demonstrated a clear dose-dependent health risk response to increasing amounts of these pollutants except at high concentrations. In addition, a number of studies examining the effects of ambient level exposure to NO2, SO2, and CO have failed to find associations with adverse health outcomes.

Comparison of effects ofin vivo nitrogen dioxide exposure starting from different periods on alveolar macrophage activity, assessed by a chemiluminescence technique in Brown-Norway rats

Nitrogen dioxide (NO2) has been extensively studied for its immune modulating effects on pulmonary cells. Alveolar macrophages (AMs) play an important role in pulmonary immunity. The Brown-Norway (BN) rat has been studied as a high-risk model of allergic diseases. In this study, BN rats were exposed to NO2 from the embryonic or weanling period (EP or WP, respectively). To evaluate the effects of NO2 exposure on pulmonary immunity, the activity levels of rat AMs were assessed as reactive oxygen species-generating capacity, measured by a chemiluminescence (CL) technique, and as cytokine-producing ability. Except for 0.2 ppm of NO2 exposure, the CL responses of AMs obtained from the WP group at 12 weeks old were suppressed significantly. Changes of the cytokine-producing levels suggest that inflammatory reactions are terminated at 12 weeks in the EP group. Correlations between the CL responses and the cytokine levels reveal that NO2 exposure may modulate the direction of AM activation. The CL technique is thought to be useful to evaluate changes in AM activity. In this study, the results suggest that, using the high-risk model of allergic diseases, NO2 exposure from the weanling period has stronger effects on AM activity.

Comparison of biocompatibility of gel-derived bioactive ceramics in macrophage culture conditions

The behaviour of rat alveolar macrophages cultured in the presence of three new gel-derived ceramic biomaterials (CaO-P2O5-SiO2 system) with slightly different chemical compositions was examined. The abilities of these three materials to stimulate alveolar macrophages were compared. Non-treated and lipopolysaccharide-treated macrophages were used as control. The level of macrophage activation was determined by nitrite and prostaglandin E2 assay and respiratory burst measurement by chemiluminescence. The results of these studies showed different macrophage responses to these three relatively similar stimuli. Two of the studied materials were shown to be potent activators of respiratory burst and prostaglandin E2 secretion without any significant release of nitric oxide. On the contrary, the material characterized as the most surface reactive strongly affected only nitric oxide generation by the cells.

Paraquat-induced formation of leukotriene B4 in rat lungs: modulation by N-acetylcysteine

The present work is focused on the formation of the inflammatory mediator leukotriene B4 (LTB4) in the lungs of paraquat (PQ)-intoxicated rats. The levels of LTB4 and the number of neutrophils in lung lavages of PQ-intoxicated rats, measured 12 h after 30 mg/kg PQ, increased significantly compared with those of control animals; administration of 50 mg/kg IP N-acetylcysteine (NAC), 8 h after PQ, inhibited this effect. The release of LTB4 from alveolar macrophages (AM) or alveolar epithelial type II cells from healthy animals incubated with PQ and/or NAC did not offer' an explanation for the effect of these chemicals on LTB4 in the bronchoalveolar lavage fluid (BALF). The PQ-enhanced, NAC-inhibited release of arachidonic acid (AA) by alveolar epithelial type II cells did, however, explain our in vivo results, when one assumes that the AM synthesize their 5-lipoxygenase products from alveolar epithelial cell-derived AA, an hypothesis demonstrated already by other researchers.

Release of aldehydes from rat alveolar macrophages exposed in vitro to low concentrations of nitrogen dioxide

This study demonstrated that aldehydes are released into the extracellular medium when alveolar macrophages (AM) are exposed to nitrogen dioxide (NO2) at concentrations that impair cell function but do not cause cell death. Butanal, glycolaldehyde, 4-hydroxynonenal, pentanal, pentenal, and hexanal were found. Dinitrophenylhydrazine (DNP) derivitization, thin layer chromatography, high performance liquid chromatography, and gas chromatography-mass spectrometry were used to identify the products. Some of the aldehydes have potential toxicity and may be responsible, in part, for altered AM function observed following NO2 exposure.

The role of free radicals and antioxidants: how do we know that they are working?

This review briefly discusses how free radicals are formed and the possible participation of free radicals in disease. The review describes the basic radical reactions and the types of products that are formed from the free-radical reactions of cellular constituents. In many cases, in vivo free-radical oxidation can be detected by measuring products that were derived from radical reactions. Since aerobic organisms generate oxygen-containing free radicals during oxygen metabolism, they carry chemicals and enzymes that reduce the threat posed by these radicals. The more common sources of in vivo free radicals are described in the article as well as the methods used by cells to protect themselves from free-radical damage. Generation of free radicals in vivo also may be the result of exposure to certain chemical agents present in the environment. Many of these agents cause pathologic changes to the exposed tissues and organs by initiating free-radical reactions.