Similar to asbestos fibers, nonregulated mineral fibers can cause malignant mesothelioma (MM). Recently, increased proportions of women and young individuals with MM were identified in southern Nevada, suggesting that environmental exposure to carcinogenic fibers was causing the development of MM. Palygorskite, a fibrous silicate mineral with a history of possible carcinogenicity, is abundant in southern Nevada. In this study, our aim was to determine whether palygorskite was contributing to the development of MM in southern Nevada. While palygorskite, in vitro, displayed some cytotoxicity toward primary human mesothelial (HM) cells and reduced their viability, the effects were roughly half of those observed when using similar amounts of crocidolite asbestos. No Balb/c (0/19) or MexTAg (0/18) mice injected with palygorskite developed MM, while 3/16 Balb/c and 13/14 MexTAg mice injected with crocidolite did. Lack of MM development was associated with a decreased acute inflammatory response, as injection of palygorskite resulted in lower percentages of macrophages (p = .006) and neutrophils (p = .02) in the peritoneal cavity 3 d after exposure compared to injection of crocidolite. Additionally, compared to mice injected with crocidolite, palygorskite-injected mice had lower percentages of M2 (tumor-promoting) macrophages (p = .008) in their peritoneal cavities when exposed to fiber for several weeks. Our study indicates that palygorskite found in the environment in southern Nevada does not cause MM in mice, seemingly because palygorskite, in vivo, fails to elicit inflammation that is associated with MM development. Therefore, palygorskite is not a likely contributor to the MM cases observed in southern Nevada.

中文翻译：

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研究坡缕石在内华达州南部间皮瘤发展中的作用：对纤维诱导的致癌性的见解。

与石棉纤维相似，不受管制的矿物质纤维也会引起恶性间皮瘤（MM）。最近，在内华达州南部发现患有MM的妇女和年轻人的比例有所增加，这表明环境暴露于致癌纤维会导致MM的发展。坡缕石是一种纤维状硅酸盐矿物，有可能致癌的历史，在内华达州南部十分丰富。在这项研究中，我们的目的是确定坡缕石是否有助于内华达州南部的MM的发展。尽管坡缕石在体外对原代人间皮（HM）细胞显示出一定的细胞毒性，并降低了它们的生存能力，但其效果大约是使用类似量的青石棉石棉时观察到的效果的一半。没有注射坡缕石的Balb / c（0/19）或MexTAg（0/18）小鼠出现MM，而3/16 Balb / c和13/14 MexTAg小鼠注射了青石棉。与注射青石棉相比，注射坡缕石导致腹膜腔内巨噬细胞（p = .006）和嗜中性白细胞（p = .02）的百分比降低，因此缺乏MM发展与急性炎症反应降低有关。此外，与注射青石棉的小鼠相比，注射坡缕石的小鼠在腹腔中暴露于纤维数周时，其腹膜腔中的M2（促肿瘤）巨噬细胞百分比较低（p = 0.008）。我们的研究表明，在内华达州南部的环境中发现的坡缕石不会在小鼠中引起MM，这似乎是因为坡缕石在体内无法引起与MM发育相关的炎症。因此，