In Vivo Pulmonary Toxicity

Little progress was made after these preliminary findings until 2004, when Lam et al. investigated the pulmonary toxicity of three types of SWNTs (raw HiPCO SWNTs, purified HiPCO SWNTs, and Ni-catalyzed arc discharge SWNTs) instilled in mice [58]. It was found that all three SWNT samples induced dose-dependent lung lesions and interstitial inflammation after 7 days. These lesions persisted and worsened after 90 days. 

Controversial results were reported by Warheit et al. in two studies [57, 65] in which rats were exposed to raw SWNTs. Cell proliferation and cytotoxicity indices indicated that exposure to SWNTs produced only transient inflammation. Histological examination of exposed animals, however, identified the development of granulomas, which were non-dose dependent, nonuniform in distribution and not progressive after 1 month. The presence of granulomas was considered inconsistent with the lack of severe lung inflammation. These two reports highlighted the need for more research on the potential pulmonary toxicity of CNTs, shifting the scientific focus towards this aim. 

Following their preliminary study in 2001 [63], Huczko et al. published a followup study in 2005 [66]. In this investigation, five different samples of MWNTs 

In summary, intratracheal instillation of CNTs has shown that their potential in eliciting adverse pulmonary effects is influenced by exposure time, CNT dose, CNT biopersistence, surface defects, and metal contamination [71, 72]. Despite the use of surfactants, all studies showed that intratracheal instillation caused major difficulties due to the agglomerative nature of CNTs in a biological environment. More realistic exposure methods, namely inhalation rather than intratracheal administration, are therefore needed for determining the pulmonary toxicity [59, 65, 73]. Several investigations have been performed by using administration different from intra- 

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Mutlu, G.M. et al. (2010) Biocompatible nanoscale dispersion of single-walled carbon nanotubes minimizes in vivo pulmonary toxicity. Nano Letters, 10 (5), 1664-1670. 

In rats, the administration of fullerene by inhalation, as nano- and microparticles generated by aerosol, does not lead to lesions and only a little increase of protein concentration in bronchoalveolar lavage fluid was obtained (Baker et al., 2007). Recently, Sayes et al. (2007) analyzed in vivo pulmonary toxicity of C60 and C60(OH)24, after intratracheal instillation in rats. They verified only transient inflammatory and cell injury effects, 1 day postexposure, without differences from water-instilled controls. No adverse lung tissue effects were measured, and the results demonstrated little or no differences in lung toxicity effects between the C60 and fiillerols, compared to controls. 

Sayes CM, Reed KL, Warheit DB (2007) Assessing toxicity of fine and nanoparticles comparing in vitro measurements to in vivo pulmonary toxicity profiles. Toxicol Sci 97(1)463-180... 

Sayes C, Marchione A, Reed K, Warheit DB (2007) Comparative pulmonary toxicity assessments of C60 water suspensions in rats Few differences in fullerene toxicity in vivo in contrast to in vitro profiles. Nano Lett. 7 2399-2403. 

The increased expression of adhesion molecules by the endothelium may activate polymorphonuclear neutrophils (PMN) in rabbits [72], During endotoxic shock, activated PMNs release their granule content and secrete both proinflammatory and cytotoxic molecules. Pickaver et al. [73] were the first to show PMN cytotoxicity against tumor cells. We showed that PMNs are toxic for PROb colon tumor cells [74] in BDEX rats. In vivo, PMNs have been implicated in the Schwartzman reaction [75], and may be involved in LPS-induced tumor necrosis. PMNs, when activated by LPS, synthesize and release NO. The role of NO in tumor growth will be discussed later. The decrease in tumor growth after intradermal injections of LPS is attributed to the induction of TNF-a secretion by PMNs both in intradermal tumors (Meth A sarcoma in BALB/c mice, MH-134 hepatoma in C3H/He mice, Lewis Lung carcinomas in C57BL/6 mice) and pulmonary Meth A metastases [76,77],... 

Boyd MR, Burka LT. In vivo studies on the relationship between target organ alkylation and the pulmonary toxicity of a chemically reactive metabolite of 4-ipomeanoI. J Pharmacol Exp Ther 1978 207(3) 687-697. 

T. Shirakawa, S. C. Ko, T. A. Gardner, J. Cheon, T. Miyamoto, A. Gotoh, L. W. Chung, and C. Kao, In vivo suppression of osteosarcoma pulmonary metastasis with intravenous osteocalcin promoter-based toxic gene therapy, Cancer Gene Ther. 5 274 (1998). 

The reaction of the inhaled particles with endogenous molecules present in the pulmonary surfactant e.g. surfactant, antioxidant molecules and proteins may determine the fate of the particles in the early steps of the pathological process. Although the silica samples considered in the present work are very pure, with the SiC>2 content great then 98%, they strongly differ in surface properties. The observed different interaction of BSA with the dusts considered is a consequence of such variability. Since the response of macrophages to silica particles may be different depending on the amount of protein adsorbed, the in vivo and/or in vitro toxicity of the silica dusts may be affected by the different affinities for pulmonary surfactant proteins. 

Although inhalational botulinum intoxication was investigated in other animal species, these studies have not provided specific data on toxin absorption. The behavior of BoNTs in the respiratory tract was only recently investigated. Park and Simpson (2003) studied the properties of pure BoNT/A neurotoxin both in vivo and in vitro using mice and pulmonary cell culture models, respectively. Mean survival times were compared in mice receiving various doses of pure BoNT/A either IN or IP. Pure BoNT/A was found to be a potent intranasal poison, although the toxicity (as determined by mean survival time) associated with IP administration was somewhat higher. Mean survival times in mice were less than 100 (IP) or 600 min (IN) after administration of 0.1 pg pure toxin 75 (IP) or 400 min (IN) for 1 pg toxin and 120 min (IN) for 10 pg toxin (Park and... 

These processes can be complemented and enhanced by the liberation of biologically active cellular mediators from intracellular compartments or from the cell membrane. Thus, it is understandable that PFTs provoke inflammatory lesions and acute organ dysfunction in vitro and in vivo, and are lethal in experimental animals. When perfused through an isolated lung, PFTs provoke profound pathophysiological alterations in the pulmonary microvasculature and cause irreversible pulmonary edema. The underlying mechanisms are complex, but include a direct toxic action on endothelial cells, and the pro-... 

The studies with 3MC and IPO discussed earlier illustrate this point. Pretreatment with 3MC shifts the target organ for IPO alkylation and toxicity in rats from the lung to the liver (21). In vitro studies demonstrate that 3MC pretreatment increases the alkylation of liver microsomes from rats, but does not affect alkylation of lung microsomes(10). This suggests that the vivo hepatic toxicity of IPO is due to increased hepatic formation of the toxic metabolite. 3MC pretreatment reduces the amount of circulating IPO, which probably accounts for the decreased pulmonary alkylation and toxicity (23). 

II. Toxic dose. Because mycotoxins are not volatile, exposure would require inhalation of aerosolized spores, mycelial fragments, or contaminated substrates. The toxic inhaled dose of mycotoxin for humans is not known. Based on experimental data from single-dose in vivo studies, Stachybotrys chartarum spores (in-tranasally in mice or intratracheally in rats) high doses (more than 30 million spores/kg) can produce pulmonary inflammation and hemorrhage. The no-effect dose in rats (3 million ores/kg) corresponds to a continuous 24-hour exposure to 2.1 million spores/m for infants, 6.6 million spores/m for a school-age child, or 15.3 million spores/m for an adult. These spore concentrations are much higher than those measured in building surveys. 

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