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Ablation of SP-A has a negative impact on the susceptibility of mice to Klebsiella pneumoniae infection after ozone exposure: sex differences.

Mikerov AN, Haque R, Gan X, Guo X, Phelps DS, Floros J - Respir. Res. (2008)

Bottom Line: We hypothesized that ablation of SP-A has a negative impact on the susceptibility of mice to Klebsiella pneumoniae infection after ozone exposure, and that sex differences in the effect of ozone do exist.We found: 1) ozone exposure followed by K. pneumoniae infection decreases survival and alveolar macrophage phagocytic function of SP-A (-/-) mice compared to filtered air exposure (p < 0.05), and females are more affected than males; 2) SP-A (-/-) mice (exposed either to ozone or FA) are more susceptible to infection with K. pneumoniae than wild type (WT) mice regarding their survival rate and macrophage phagocytic function; the phagocytic function of FA SP-A(-/-) is similar to that of ozone exposed WT. 3) ozone exposure appears to increase infiltration of PMNs, total protein, and SP-A oxidation in WT mice; infiltration of PMNs and total protein oxidation appears to be more pronounced in female mice in response to ozone; 4) ozone exposure increases SP-A oxidation in WT females significantly more than in males.Absence (i.e. ablation of SP-A in SP-A (-/-) mice) or reduction of functional activity of SP-A (i.e. oxidation of SP-A in WT mice) increases the susceptibility of mice to experimental pneumonia after ozone exposure, and in both cases females are more affected by ozone exposure than males.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Penn State Center for Host defense, Inflammation, and Lung Disease Research, Department of Pediatrics, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA. a_mikerov@mail.ru

ABSTRACT

Background: Surfactant protein A (SP-A) enhances phagocytosis of bacteria, including Klebsiella pneumoniae, by alveolar macrophages. Ozone, a major air pollutant, can cause oxidation of surfactant and may influence lung immune function. Immune function may also be affected by sex-specific mechanisms. We hypothesized that ablation of SP-A has a negative impact on the susceptibility of mice to Klebsiella pneumoniae infection after ozone exposure, and that sex differences in the effect of ozone do exist.

Methods: Male and female SP-A (-/-) mice on the C57BL/6J background were exposed to ozone or to filtered air (FA) used as a control and then infected intratracheally with K. pneumoniae bacteria. Survival rate was monitored during a 14-day period. In addition, protein oxidation levels and in vivo phagocytosis were checked 1 h after inoculation of PBS used as a sham control and after inoculation of K. pneumoniae bacteria in PBS, respectively.

Results: We found: 1) ozone exposure followed by K. pneumoniae infection decreases survival and alveolar macrophage phagocytic function of SP-A (-/-) mice compared to filtered air exposure (p < 0.05), and females are more affected than males; 2) SP-A (-/-) mice (exposed either to ozone or FA) are more susceptible to infection with K. pneumoniae than wild type (WT) mice regarding their survival rate and macrophage phagocytic function; the phagocytic function of FA SP-A(-/-) is similar to that of ozone exposed WT. 3) ozone exposure appears to increase infiltration of PMNs, total protein, and SP-A oxidation in WT mice; infiltration of PMNs and total protein oxidation appears to be more pronounced in female mice in response to ozone; 4) ozone exposure increases SP-A oxidation in WT females significantly more than in males.

Conclusion: Absence (i.e. ablation of SP-A in SP-A (-/-) mice) or reduction of functional activity of SP-A (i.e. oxidation of SP-A in WT mice) increases the susceptibility of mice to experimental pneumonia after ozone exposure, and in both cases females are more affected by ozone exposure than males.

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Total protein oxidation in BAL of FA-exposed and ozone-exposed WT male and female mice. Experimental design was as described in Figure 5. After the mouse lungs were lavaged, BAL was centrifuged, and the supernatant was used for the estimation of total protein concentration in BAL (6A) and for total oxidized protein analysis (6B) as described in Methods. An aliquot of the same supernatant analyzed in Figure 5 was also used here. The OD × mm2 values were calculated for each sample. FA-exposed groups are shown with opened bars, and ozone-exposed groups – with solid bars. Significance between different groups of mice is shown with connecting lines above the respective bars. Statistical analysis was performed with a t-test and the differences were considered as significant if p < 0.05.
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Figure 6: Total protein oxidation in BAL of FA-exposed and ozone-exposed WT male and female mice. Experimental design was as described in Figure 5. After the mouse lungs were lavaged, BAL was centrifuged, and the supernatant was used for the estimation of total protein concentration in BAL (6A) and for total oxidized protein analysis (6B) as described in Methods. An aliquot of the same supernatant analyzed in Figure 5 was also used here. The OD × mm2 values were calculated for each sample. FA-exposed groups are shown with opened bars, and ozone-exposed groups – with solid bars. Significance between different groups of mice is shown with connecting lines above the respective bars. Statistical analysis was performed with a t-test and the differences were considered as significant if p < 0.05.

Mentions: Total protein concentration was significantly increased in the BAL from males in response to ozone, as we showed before [42], but no significant difference was observed in samples from female mice (Figure 6A). Total protein oxidation appeared to be increased (albeit not significantly) in BAL of ozone-exposed mice with females showing a smaller but significant increase in the levels of oxidized protein in BAL compared to males (Figure 6B). Analysis of the total SP-A (monomer, dimer, and both) demonstrated that SP-A concentration in BAL appeared to increase in response to ozone, and that the values from females were higher than those from males (p < 0.05) for all monomer, dimer, and total SP-A for ozone-exposed mice (Figure 7A). Oxidized SP-A dimer analysis (only dimer was found to be oxidized in mouse SP-A) revealed that ozone increased the oxidation of SP-A dimer (with p < 0.05 for females only) (Figure 7B and 7C). To assess the net effect of ozone on the total protein oxidation and SP-A oxidation in mouse BAL, the percent of ozone/FA values were calculated. The analysis revealed that ozone appeared to increase oxidation of the total protein in BAL, albeit not significantly. However, ozone specifically increased oxidation of SP-A (p < 0.05 for females only) with female mice showing a significantly (p < 0.05) higher level of SP-A oxidation than males (Figure 8).


Ablation of SP-A has a negative impact on the susceptibility of mice to Klebsiella pneumoniae infection after ozone exposure: sex differences.

Mikerov AN, Haque R, Gan X, Guo X, Phelps DS, Floros J - Respir. Res. (2008)

Total protein oxidation in BAL of FA-exposed and ozone-exposed WT male and female mice. Experimental design was as described in Figure 5. After the mouse lungs were lavaged, BAL was centrifuged, and the supernatant was used for the estimation of total protein concentration in BAL (6A) and for total oxidized protein analysis (6B) as described in Methods. An aliquot of the same supernatant analyzed in Figure 5 was also used here. The OD × mm2 values were calculated for each sample. FA-exposed groups are shown with opened bars, and ozone-exposed groups – with solid bars. Significance between different groups of mice is shown with connecting lines above the respective bars. Statistical analysis was performed with a t-test and the differences were considered as significant if p < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC2655296&req=5

Figure 6: Total protein oxidation in BAL of FA-exposed and ozone-exposed WT male and female mice. Experimental design was as described in Figure 5. After the mouse lungs were lavaged, BAL was centrifuged, and the supernatant was used for the estimation of total protein concentration in BAL (6A) and for total oxidized protein analysis (6B) as described in Methods. An aliquot of the same supernatant analyzed in Figure 5 was also used here. The OD × mm2 values were calculated for each sample. FA-exposed groups are shown with opened bars, and ozone-exposed groups – with solid bars. Significance between different groups of mice is shown with connecting lines above the respective bars. Statistical analysis was performed with a t-test and the differences were considered as significant if p < 0.05.
Mentions: Total protein concentration was significantly increased in the BAL from males in response to ozone, as we showed before [42], but no significant difference was observed in samples from female mice (Figure 6A). Total protein oxidation appeared to be increased (albeit not significantly) in BAL of ozone-exposed mice with females showing a smaller but significant increase in the levels of oxidized protein in BAL compared to males (Figure 6B). Analysis of the total SP-A (monomer, dimer, and both) demonstrated that SP-A concentration in BAL appeared to increase in response to ozone, and that the values from females were higher than those from males (p < 0.05) for all monomer, dimer, and total SP-A for ozone-exposed mice (Figure 7A). Oxidized SP-A dimer analysis (only dimer was found to be oxidized in mouse SP-A) revealed that ozone increased the oxidation of SP-A dimer (with p < 0.05 for females only) (Figure 7B and 7C). To assess the net effect of ozone on the total protein oxidation and SP-A oxidation in mouse BAL, the percent of ozone/FA values were calculated. The analysis revealed that ozone appeared to increase oxidation of the total protein in BAL, albeit not significantly. However, ozone specifically increased oxidation of SP-A (p < 0.05 for females only) with female mice showing a significantly (p < 0.05) higher level of SP-A oxidation than males (Figure 8).

Bottom Line: We hypothesized that ablation of SP-A has a negative impact on the susceptibility of mice to Klebsiella pneumoniae infection after ozone exposure, and that sex differences in the effect of ozone do exist.We found: 1) ozone exposure followed by K. pneumoniae infection decreases survival and alveolar macrophage phagocytic function of SP-A (-/-) mice compared to filtered air exposure (p < 0.05), and females are more affected than males; 2) SP-A (-/-) mice (exposed either to ozone or FA) are more susceptible to infection with K. pneumoniae than wild type (WT) mice regarding their survival rate and macrophage phagocytic function; the phagocytic function of FA SP-A(-/-) is similar to that of ozone exposed WT. 3) ozone exposure appears to increase infiltration of PMNs, total protein, and SP-A oxidation in WT mice; infiltration of PMNs and total protein oxidation appears to be more pronounced in female mice in response to ozone; 4) ozone exposure increases SP-A oxidation in WT females significantly more than in males.Absence (i.e. ablation of SP-A in SP-A (-/-) mice) or reduction of functional activity of SP-A (i.e. oxidation of SP-A in WT mice) increases the susceptibility of mice to experimental pneumonia after ozone exposure, and in both cases females are more affected by ozone exposure than males.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Penn State Center for Host defense, Inflammation, and Lung Disease Research, Department of Pediatrics, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA. a_mikerov@mail.ru

ABSTRACT

Background: Surfactant protein A (SP-A) enhances phagocytosis of bacteria, including Klebsiella pneumoniae, by alveolar macrophages. Ozone, a major air pollutant, can cause oxidation of surfactant and may influence lung immune function. Immune function may also be affected by sex-specific mechanisms. We hypothesized that ablation of SP-A has a negative impact on the susceptibility of mice to Klebsiella pneumoniae infection after ozone exposure, and that sex differences in the effect of ozone do exist.

Methods: Male and female SP-A (-/-) mice on the C57BL/6J background were exposed to ozone or to filtered air (FA) used as a control and then infected intratracheally with K. pneumoniae bacteria. Survival rate was monitored during a 14-day period. In addition, protein oxidation levels and in vivo phagocytosis were checked 1 h after inoculation of PBS used as a sham control and after inoculation of K. pneumoniae bacteria in PBS, respectively.

Results: We found: 1) ozone exposure followed by K. pneumoniae infection decreases survival and alveolar macrophage phagocytic function of SP-A (-/-) mice compared to filtered air exposure (p < 0.05), and females are more affected than males; 2) SP-A (-/-) mice (exposed either to ozone or FA) are more susceptible to infection with K. pneumoniae than wild type (WT) mice regarding their survival rate and macrophage phagocytic function; the phagocytic function of FA SP-A(-/-) is similar to that of ozone exposed WT. 3) ozone exposure appears to increase infiltration of PMNs, total protein, and SP-A oxidation in WT mice; infiltration of PMNs and total protein oxidation appears to be more pronounced in female mice in response to ozone; 4) ozone exposure increases SP-A oxidation in WT females significantly more than in males.

Conclusion: Absence (i.e. ablation of SP-A in SP-A (-/-) mice) or reduction of functional activity of SP-A (i.e. oxidation of SP-A in WT mice) increases the susceptibility of mice to experimental pneumonia after ozone exposure, and in both cases females are more affected by ozone exposure than males.

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Related in: MedlinePlus