Incomplete lung recovery following sub-acute inhalation of combustion-derived ultrafine particles in mice.

BACKGROUND: Particulate matter (PM) is one of the six criteria pollutant classes for which National Ambient Air Quality Standards have been set by the United States Environmental Protection Agency. Exposures to PM have been correlated with increased cardio-pulmonary morbidity and mortality. Butadiene soot (BDS), generated from the incomplete combustion of 1,3-butadiene (BD), is both a model PM mixture and a real-life example of a petrochemical product of incomplete combustion. There are numerous events, including wildfires, accidents at refineries and tank car explosions that result in sub-acute exposure to high levels of airborne particles, with the people exposed facing serious health problems. These real-life events highlight the need to investigate the health effects induced by short-term exposure to elevated levels of PM, as well as to assess whether, and if so, how well these adverse effects are resolved over time. In the present study, we investigated the extent of recovery of mouse lungs 10 days after inhalation exposures to environmentally-relevant levels of BDS aerosols had ended. METHODS: Female BALB/c mice exposed to either HEPA-filtered air or to BDS (5 mg/m(3) in HEPA filtered air, 4 h/day, 21 consecutive days) were sacrificed immediately, or 10 days after the final BDS exposure. Bronchoalveolar lavage fluid (BALF) was collected for cytology and cytokine analysis. Lung proteins and RNA were extracted for protein and gene expression analysis. Lung histopathology evaluation also was performed. RESULTS: Sub-acute exposures of mice to hydrocarbon-rich ultrafine particles induced: (1) BALF neutrophil elevation; (2) lung mucosal inflammation, and (3) increased BALF IL-1ß concentration; with all three outcomes returning to baseline levels 10 days post-exposure. In contrast, (4) lung connective tissue inflammation persisted 10 days post-exposure; (5) we detected time-dependent up-regulation of biotransformation and oxidative stress genes, with incomplete return to baseline levels; and (6) we observed persistent particle alveolar load following 10 days of recovery. CONCLUSION: These data show that 10 days after a 21-day exposure to 5 mg/m(3) of BDS has ended, incomplete lung recovery promotes a pro-biotransformation, pro-oxidant, and pro-inflammatory milieu, which may be a starting point for potential long-term cardio-pulmonary effects.

Heat-shock-induced enhanced reactivation of UV-irradiated Herpesvirus.

The objective of this study was to compare the ability of heat shock (HS) with that of another type of cellular stress, UV irradiation, to cause the induction of enhanced viral reactivation, a process that may represent an SOS-type repair process in mammalian cells. Studies performed to evaluate the effect of HS on growth of Vero cells revealed that HS at 45 degrees C for 45 min caused inhibition of cell growth similar to that caused by UV irradiation at 12 J/m2, but this inhibition was not observed at HS treatment for 5-15 min, or at a UV fluence of 2 J/m2. Enhanced reactivation of UV-irradiated Herpesvirus was observed in cells which had been pretreated by HS for greater than 30 min or UV at 12 J/m2. The synthesis of new proteins following HS for 15 and 45 min and UV at 12 J/m2 was examined by [35S]methionine-labeling experiments. The new synthesis of two HS proteins with molecular weights of 46 000 and 78 000 was induced by both levels of HS, but to a much greater extent at the high dose. These proteins were not detected in response to UV irradiation. These results indicate that, like UV irradiation, HS at levels inhibitory to cell growth induced enhanced viral reactivation in Vero cells. The results also suggest that at least two proteins in the HS protein family are not necessary for this response to occur.

Age-dependent changes in prevalence, size and proliferation of arterial lesions in cockerels. II. Carcinogen-associated lesions.

Age-dependent changes were determined in the prevalence, frequency, size and proliferative activity of aortic lesions arising in cockerels injected weekly with the polycyclic hydrocarbon carcinogen, 7,12-dimethylbenz (a) anthracene (DMBA). Starting at 4 weeks of age, groups of 6 animals received weekly i.m. injections of DMBA (10 mg/kg body weight) dissolved in dimethylsulfoxide (DMSO). Controls were injected with DMSO. Animals were sacrificed (DMSO). Controls were injected with DMSO. Animals were sacrificed at 4 week intervals between 8-20 weeks of age. Microscopic lesions were observed in the abdominal aortas of all animals regardless of age or treatment. At no time point were there statistically significant differences in the prevalence or frequency of lesions between DMBA-treated animals and age-matched controls. In addition, lesion areas were log-normally distributed in all groups. However, DMBA exposure elicited 2 sets of changes not seen in controls. Carcinogen treatment accelerated the time and rate of appearance of large lesions. Eight week old DMBA-treated animals displayed lesion sizes comparable to those seen in 20 week old controls. Continued exposure to DMBA resulted in sharp increases in lesion size up to 20 weeks of age. Between 12-20 weeks lesion size increased, in a nearly linear fashion, by 12X in DMBA-treated animals but only by 2X in controls. There also was a burst of lesion cell proliferation in cockerels after 12 weeks of DMBA treatment. No equivalent increase in proliferation was seen in lesion cells in controls or in medial cells of either experimental or control animals. These results demonstrate that chronic carcinogen exposure results in the accelerated development of pre-existing "spontaneous' lesions rather than the initiation of new lesions. In addition, the results indicate that lesions are not homogeneous regarding their response to proliferative stimuli. This suggests that within a lesion there may exist subpopulations of cells which are more capable of proliferating in response to DMBA, and presumably to other agents, than are the majority of lesion cells.

Age-dependent changes in prevalence, size and proliferation of arterial lesions in cockerels. I. Spontaneous lesions.

Age-dependent changes were determined in the prevalence, size and proliferation of early spontaneous aortic lesions in white leghorn cockerels. Groups of 6 animals received weekly intramuscular injections of dimethyl sulfoxide (DMSO) or remained uninjected. They were sacrificed at 6, 8, 12, 16, 20 and 38 weeks of age. Lesions were observed microscopically in all animals 8 weeks of age and older. They appeared in 20-30% of the aortic segments until 16 weeks of age and in 60% of the segments thereafter. The presence of a long single lesion along the aortic segments until 16 weeks of age and in 60% of the segments thereafter. The presence of a long single lesion along the aortic length was revealed by sectioning serially, at 50 micrometers intervals, 10-20 mm lengths of lesion-containing aorta. Between 8 and 20 weeks of age, lesion cross-sectional area increased by a factor of 2.4 while lesion volume index increased by a factor of 6. Similar patterns of proliferation were observed at each time point between lesion cells and those in the underlying media. Labeling indices of media and lesion cells were highest when the animals were growing rapidly and lowest when the animals reached full size. The results indicate that in the cockerel: (1) spontaneous lesions increase in depth and extend radially at a low constant level between 8 and 20 weeks of age and increase markedly in length between 16 and 20 weeks, (2) lesion cell proliferation is sufficient to account for the observed increase in lesion size, and (3) proliferation of lesion cells and medial cells may be governed by the same control mechanism(s).