The Signal Transducer and Activator of Transcription 1 (STAT1) Inhibits Mitochondrial Biogenesis in Liver and Fatty Acid Oxidation in Adipocytes

The transcription factor STAT1 plays a central role in orchestrating responses to various pathogens by activating the transcription of nuclear-encoded genes that mediate the antiviral, the antigrowth, and immune surveillance effects of interferons and other cytokines. In addition to regulating gene expression, we report that STAT1-/- mice display increased energy expenditure and paradoxically decreased release of triglycerides from white adipose tissue (WAT). Liver mitochondria from STAT1-/- mice show both defects in coupling of the electron transport chain (ETC) and increased numbers of mitochondria. Consistent with elevated numbers of mitochondria, STAT1-/- mice expressed increased amounts of PGC1α, a master regulator of mitochondrial biogenesis. STAT1 binds to the PGC1α promoter in fed mice but not in fasted animals, suggesting that STAT1 inhibited transcription of PGC1α. Since STAT1-/-mice utilized more lipids we examined white adipose tissue (WAT) stores. Contrary to expectations, fasted STAT1-/- mice did not lose lipid from WAT. β-adrenergic stimulation of glycerol release from isolated STAT1-/- WAT was decreased, while activation of hormone sensitive lipase was not changed. These findings suggest that STAT1-/- adipose tissue does not release glycerol and that free fatty acids (FFA) re-esterify back to triglycerides, thus maintaining fat mass in fasted STAT1-/- mice

Differential Pulmonary Effects of CoO and La2O3 Metal Oxide Nanoparticle Responses During Aerosolized Inhalation in Mice

Background: Although classified as metal oxides, cobalt monoxide (CoO) and lanthanum oxide (La2O3) nanoparticles, as representative transition and rare earth oxides, exhibit distinct material properties that may result in different hazardous potential in the lung. The current study was undertaken to compare the pulmonary effects of aerosolized whole body inhalation of these nanoparticles in mice. Results: Mice were exposed to filtered air (control) and 10 or 30 mg/m3 of each particle type for 4 days and then examined at 1 h, 1, 7 and 56 days post-exposure. The whole lung burden 1 h after the 4 day inhalation of CoO nanoparticles was 25 % of that for La2O3 nanoparticles. At 56 days post exposure, \u3c 1 % of CoO nanoparticles remained in the lungs; however, 22–50 % of the La2O3 nanoparticles lung burden 1 h post exposure was retained at 56 days post exposure for low and high exposures. Significant accumulation of La2O3 nanoparticles in the tracheobronchial lymph nodes was noted at 56 days post exposure. When exposed to phagolysosomal simulated fluid, La nanoparticles formed urchin-shaped LaPO4 structures, suggesting that retention of this rare earth oxide nanoparticle may be due to complexation of cellular phosphates within lysosomes. CoO nanoparticles caused greater lactate dehydrogenase release in the bronchoalveolar fluid (BALF) compared to La2O3 nanoparticles at 1 day post exposure, while BAL cell differentials indicate that La2O3 nanoparticles generated more inflammatory cell infiltration at all doses and exposure points. Histopathological analysis showed acute inflammatory changes at 1 day after inhalation of either CoO or La2O3 nanoparticles. Only the 30 mg/m3 La2O3 nanoparticles exposure caused chronic inflammatory changes and minimal fibrosis at day 56 post exposure. This is in agreement with activation of the NRLP3 inflammasome after in vitro exposure of differentiated THP-1 macrophages to La2O3 but not after CoO nanoparticles exposure. Conclusion: Taken together, the inhalation studies confirmed the trend of our previous sub-acute aspiration study, which reported that CoO nanoparticles induced more acute pulmonary toxicity, while La2O3 nanoparticles caused chronic inflammatory changes and minimal fibrosis

In vitro toxicological evaluation of surgical smoke from human tissue

Abstract Background Operating room personnel have the potential to be exposed to surgical smoke, the by-product of using electrocautery or laser surgical device, on a daily basis. Surgical smoke is made up of both biological by-products and chemical pollutants that have been shown to cause eye, skin and pulmonary irritation. Methods In this study, surgical smoke was collected in real time in cell culture media by using an electrocautery surgical device to cut and coagulate human breast tissues. Airborne particle number concentration and particle distribution were determined by direct reading instruments. Airborne concentration of selected volatile organic compounds (VOCs) were determined by evacuated canisters. Head space analysis was conducted to quantify dissolved VOCs in cell culture medium. Human small airway epithelial cells (SAEC) and RAW 264.7 mouse macrophages (RAW) were exposed to surgical smoke in culture media for 24 h and then assayed for cell viability, lactate dehydrogenase (LDH) and superoxide production. Results Our results demonstrated that surgical smoke-generated from human breast tissues induced cytotoxicity and LDH increases in both the SAEC and RAW. However, surgical smoke did not induce superoxide production in the SAEC or RAW. Conclusion These data suggest that the surgical smoke is cytotoxic in vitro and support the previously published data that the surgical smoke may be an occupational hazard to healthcare workers

Differential pulmonary effects of CoO and La2O3 metal oxide nanoparticle responses during aerosolized inhalation in mice.

BackgroundAlthough classified as metal oxides, cobalt monoxide (CoO) and lanthanum oxide (La2O3) nanoparticles, as representative transition and rare earth oxides, exhibit distinct material properties that may result in different hazardous potential in the lung. The current study was undertaken to compare the pulmonary effects of aerosolized whole body inhalation of these nanoparticles in mice.ResultsMice were exposed to filtered air (control) and 10 or 30 mg/m(3) of each particle type for 4 days and then examined at 1 h, 1, 7 and 56 days post-exposure. The whole lung burden 1 h after the 4 day inhalation of CoO nanoparticles was 25 % of that for La2O3 nanoparticles. At 56 days post exposure, < 1 % of CoO nanoparticles remained in the lungs; however, 22-50 % of the La2O3 nanoparticles lung burden 1 h post exposure was retained at 56 days post exposure for low and high exposures. Significant accumulation of La2O3 nanoparticles in the tracheobronchial lymph nodes was noted at 56 days post exposure. When exposed to phagolysosomal simulated fluid, La nanoparticles formed urchin-shaped LaPO4 structures, suggesting that retention of this rare earth oxide nanoparticle may be due to complexation of cellular phosphates within lysosomes. CoO nanoparticles caused greater lactate dehydrogenase release in the bronchoalveolar fluid (BALF) compared to La2O3 nanoparticles at 1 day post exposure, while BAL cell differentials indicate that La2O3 nanoparticles generated more inflammatory cell infiltration at all doses and exposure points. Histopathological analysis showed acute inflammatory changes at 1 day after inhalation of either CoO or La2O3 nanoparticles. Only the 30 mg/m(3) La2O3 nanoparticles exposure caused chronic inflammatory changes and minimal fibrosis at day 56 post exposure. This is in agreement with activation of the NRLP3 inflammasome after in vitro exposure of differentiated THP-1 macrophages to La2O3 but not after CoO nanoparticles exposure.ConclusionTaken together, the inhalation studies confirmed the trend of our previous sub-acute aspiration study, which reported that CoO nanoparticles induced more acute pulmonary toxicity, while La2O3 nanoparticles caused chronic inflammatory changes and minimal fibrosis

Total triglycerides are increased in <i>STAT1</i>^<i>-/-</i> WAT.

<p>a. Total and b. newly synthesized triglycerides and c. the percent of the newly synthesized palmitate bound to triglyceride in tissues isolated from <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> mice that were treated with ²H₂O. Values are the mean ± SEM, * presents p < 0.05 as measured by Student T-test (compared <i>STAT1</i>^<i>+/+</i> liver tissue to <i>Stat1</i>^<i>-/-</i> liver tissue, <i>STAT1</i>^<i>+/+</i> white adipose tissue to <i>STAT1</i>^<i>-/-</i> white adipose tissue and WT muscle to <i>STAT1</i>^<i>-/-</i> muscle for n = 4 mice per group).</p

Fasted <i>STAT1</i>^<i>-/-</i> mice have defective lipolysis of WAT.

<p>a. <i>STAT1</i>^<i>+/+</i> (left panel) and <i>STAT1</i>^<i>-/-</i> mice (right panel) were fasted and white adipose tissue depots were photographed. The images shown are representative of n = 5, 8–10 week old mice per group. b. Weight of subcutaneous and gonadal fat from <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> 24 h fasted mice. n = 4 8–10 week old male mice per group. c. H&E stains of subcutaneous fat from <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> mice were analyzed for d. size (in microns). The values represent mean size of cells (mm³) ± SEM for n = 6 mice per group. e. Quantification of the number of fat cells per mm³ from H&E stains of subcutaneous fat from <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> mice. * represents p < 0.05, Student’s T-test f. Oil Red O staining of liver from fed or fasted <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> mice. The images shown are representative of n = 4, 8–10 week old male mice per group. g. Liver triglyceride concentrations in <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> mice. The values represent mean ± SEM for n = 9 male 8–10 week old mice per group, * Significantly different p < 0.05, Student’s T-test. h. Glycerol release was measured in mature adipocytes that were isolated from subcutaneous fat and treated with various doses of isoproterenol or forskolin. n = 4, 12 week old male mice per group. The effect of genotype is significant at p<0.001; The genotype-concentration interaction is significant at p<0.05 for isoproterenol and at p<0.01 for forskolin. (<b>I</b>) Western blot and densitometric quantification of isoproterenol and forskolin induced phosphorylation of HSL normalized to total HSL.</p

<i>STAT1</i>^<i>-/-</i> mice display increased energy expenditure during starvation.

<p>The rates of a. energy expenditure (EE) and respiratory quotient (RER) were measured in mice over a 24 h period. The area under the circadian curves is shown to the right of the each figure. Values are the mean ± SEM, *** P<0.05 as determined by ANOVA with Bonferoni’s correction for multiple testing. b. Body composition of 24 h fasted <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> mice. Values are the mean ± SEM, * represents < 0.05. n = 6 mice per group.</p

<i>STAT1</i>^<i>-/-</i> mice display increased mitochondrial biogenesis in liver.

<p>a. Amounts of PGC1α mRNA were measured by qRT-PCR and quantitated relative to tubulin in livers of fed or fasted <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> mice. Values were normalized to <i>STAT1</i>^<i>+/+</i> fed. * Significantly different p< 0.05(<i>STAT1</i>^<i>+/+</i> fed vs. <i>STAT1</i>^<i>+/+</i> fasted and <i>STAT1</i>^<i>+/+</i> fed vs. <i>STAT1</i>^<i>-/-</i> fed) as determined by two-way ANOVA + Holm-Sidak’s post-test, n = 5, 8–10 week old male mice per group. b. Mitochondrial DNA (ND4, ND6, Cytb, Cox1 and ATPase6) in livers of <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> mice was quantitated relative to actin DNA and normalized to <i>STAT1</i>^<i>+/+</i>. * Significantly different p< 0.05, Student’s T-test, correction for multiple testing c. Amount of mitochondrial protein in <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> livers, which was normalized to the weight of the liver. d. Number of mitochondria in <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> livers. n = 3 mice. * Significantly different p < 0.05, Student’s T-test. e. Mitochondrial DNA from <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> hearts. f. Amounts of mitochondrial RNAs in hearts in <i>STAT1</i>^<i>+/+</i> and <i>STAT1</i>^<i>-/-</i> mice. n = 6 mice per group.</p