Synchrotron microradiography study on acute lung injury of mouse caused by PM2.5 aerosols
Introduction
The increasing mortality and morbidity due to cardiopulmonary complications are attributed to elevated concentration levels of ambient particulate matters, in particular, of small inhalable particles [1]. Therefore, it is essential to understand in detail the mortality mechanism induced by such fine particles. Many reports suggest that PM2.5 induce reactive oxygen species (ROS) and inflammatory mediators, resulting in vascular permeability changes, airway constriction and tissue injury [2], [3]. The transition metal ions and peroxides in aerosols can induce free radicals and cause both cytotoxicity and a strong oxidation response [4]. Based on the previous report [5], it is found that the main acute effects of PM are due to soluble ions. Shanghai as one of most quickly developing cities in the world in economics, its energy exhausts are also raised quickly. The Chinese biggest iron plant—Baoshan steel plant and electronic power plants make two of the main contributions to PM2.5 in Shanghai. Fe and Zn are the two main transition elements in PM2.5 and high SO2 (from coal burning) even make those aerosols more toxic to our health [3]. Those soluble metal constituents of residual oil fly ash (ROFA) particles can enhance the sensitization of lung injury [6]. As PM2.5 collected from the industrial city—Shanghai contains relatively higher transition elements for instance, Fe, Zn, etc. [7], and higher sulfates [8], it is important to study the effects of the main transition compositions FeSO4 and ZnSO4 in PM2.5 induced acute pneumonia process.
Many studies related to pneumonia and cytotoxicity were carried out on the histopathological examination of lung section [9], [10], [11]. Usually, in those previous work of toxicological studies on tissues, performed by optical microscopy and the scanning proton microprobe [7], only thin tissue samples (<50 μm) excised from killed rats [10], [12] were used on some respiratory function tests [13] and on analyzing the structural changes [10]. Our present work proves that such critical limitation can be lifted by using edge-enhanced microradiographs with high energy of X-rays which can penetrate a mouse. The high intensity of X-rays makes it possible to achieve high resolution in a short time, for instance, 3 ms or less, as what required for imaging a live mouse without observed damage [14], [15]. Here, it is important to use this method in vivo to monitor acute pulmonary toxicity after the mouse intratracheally instilled as the PM2.5 toxic effect is a developing process [16]. Combining those studied results of the transition element Fe, Zn effects on lung epithelial cultured cells [17] with this studying result on lung tissue structure, it may understand more about Fe, Zn toxic effects in the industrial city PM2.5.
Section snippets
Aerosols sampling
PM2.5 samples were collected by a stacked filter air sampler at the Baoshan area which is one of the industrial districts in Shanghai. The PM2.5 aerosols were collected on Teflon filters at 6.5 m above ground at a flow rate of 78 l/min. Each sample required ∼360 h by a middle flux air sampler and all aerosol samples were collected during the period of September–November 2003.
Elemental analysis
The elemental analysis for PM2.5 was carried out by a VG X7 ICP-MS instrument (Thermo electron corporation) and at least 16
Elemental contents of PM2.5
The PM2.5 solution used for instillation was analyzed, as already mentioned, by X7 ICP-MS. The results are shown in Table 1. It is clear that the concentration of transition elements (Fe, Zn) is much higher than others (Cr, Ni, Cu, Pb, etc.). It can also be found that higher S in Shanghai PM2.5. Furthermore, Fe sulfate is one of main compositions in Fe contained PM2.5 in the previous studies [8], [20]. The higher content of transition metal Fe, Zn sulfates in Shanghai PM2.5 may be play
Conclusion
In conclusion, the synchrotron X-ray microradiographs observed in vivo show much high resolution which can monitor mouse hemorrhage process. By that un-uniformity of appearance of lung texture and hemorrhage spots with a size of <0.5 mm can be found for groups exposed to toxin solutions but not in saline solution. The hemorrhage spots and hemorrhage lines appeared in the group of mice instilled by solution of PM2.5 + FeSO4 + ZnSO4 were more than the ones in other groups of mice. FeSO4 induced more
Acknowledgements
This work was supported by grants from Shanghai Nature Science Foundation of China (03ZR14111), a Major Project of Knowledge Innovation Program of Chinese Academy of Sciences (Contract No. KJCXZ-SW-No1) and a Major Project of the National Natural Science Foundation of China (Grant No. 10496182).
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