| [Background] Cardiovascular disease (CVD) is the single leading cause of air pollution-mediated morbidity and mortality. The public cardiovascular health burdens on a global scale deriving from the ubiquitous and modifiable risks of air pollution are enormous. But how might pollutant matter (PM) induce cardiovascular compromises? Systemic inflammation and oxidative stress were proved to play critical roles in the pathogenesis, development and prognosis of CVD. Recently, effects of air pollution on the inflammation of adipose tissues have been an emerging focus all over the world. Whether inflammation of EAT is one of the predominant mechanisms of the CVD remains uncertain. Numerous researches suggested that EAT was not only a passive fat depot but an important para-endocrine and endocrine organs with very active metabolism and a source of abundant adipokines. Additionally, perirenal fat can release cytokines such as angiotensin and leptin, which may increase the renal arteries resistance and lead to refractory hypertension. To our knowledge, however, the effects of exposure to concentrated ambient particulates (CAPs) and/or ozone (O3) on EAT and perirenal fat were rarely investigated before and not well understood.[Objective] The aim of this study was to determine the characteristics of EAT and perirenal fat, examine the white and brown adipose tissues specific genes expression alteration and assess the inflammation and oxidative stress in EAT and perirenal adipose tissue in response to the short-term CAPs and/or O3exposure in a model of high-fructose rats.[Methods] Eight-week-old male Sprague Dawley rats were fed on normal diet (ND) or high-fructose chow (HF) for eight weeks, respectively. And then they were randomly assigned to CAPs and/or O3exposure by eight groups (ND-AIR, ND-CAPs, ND-O3, ND-CAPs/O3; and HF-AIR, HF-CAPs, HF-O3, HF-CAPs/O3, n=8per group) for two weeks. Pathological technologies, such as hematoxylin and eosin (H.E.) staining, transmission electron microscopy (TEM), and total RNA extraction and quantitative real-time PCR were performed to define the characteristics of the EAT and perirenal fat. Additionally, white and brown adipose tissues specific genes expression were analyzed by quantitative real-time PCR to test whether short-term exposure of CAP and/or O3leads to the genes expression alteration in EAT and perirenal fat. Finally, to evaluate the inflammation and oxidative stress in response to short-term exposure of CAP and/or O3in EAT and perirenal fat, we performed enzyme linked immunosorbent assay (ELISA) to measure the adiponectin level in the supernatant of adipose tissues, immunohistochemical staining to calculate the CD68+macrophages infiltration, transmission electron microscopy (TEM) to assess the in situ mitochondria change, and quantitative real-time PCR to determine the inflammatory genes expression, together with immunofluorescence staining and extraction of protein and Western blotting to analyze the iNOS signals and protein level.[Results] EAT and perirenal fat depots have white color in gross, large unilocular cells, round and eccentric nuclei, less mitochondrias and lipid droplets than brown adipose tissue, high expression of white adipose tissue specific genes (Dpt and Hoxc9) and low brown adipose tissue specific genes mRNA levels{UCP1, PGC-1α, Cidea, C/EBPβ and Dio2), which suggestes that EAT and perirenal fat depots are both white adipose tissues. Interestingly, EAT is dramatically different from other white adipose tissues like visceral adipose depots, with much smaller in size, and higher mRNA levels of UCP-1, PGC-1α and Cidea expression than perirenal and omental adipose tissue (p<0.05). Brown adipose tissue specific genes, such as UCP1,PGC-1α, Cidea, C/EBPβ and Dio2, were found several hundreds folds lower in EAT and perirenal fat than in brown adipose tissue (p<0.001), while the white adipose tissue specific genes expression (Dpt and Hoxc9) in EAT and perirenal fat was almost the same as in other white adipose tissue (p>0.05). Another interesting observation made in this study was that brown adipose tissue specific genes expression of UCP1,PGC-1, and Cidea in EAT was nearly10folds higher than in perirenal and visceral fat, which may suggest that EAT has some function like brown adipose tissue (p<0.05). After air pollution exposure, the relative mRNA levels of UCP1,PGC-1α, Cidea were down-regulated in ND groups, but there was no statistically significant difference among the4groups (p>0.05). As for the HF groups, significantly down-regulated alterations were found in response to CAP and or O3exposure (p<0.001). To our surprise, it was not HF-CAPs/03but HF-CAPs group showed the lowest brown adipose tissue specific genes expression compared with all other7groups (p<0.05). Brown adipose tissue specific genes alterations had almost the same trend in perirenal fat as in EAT. Dpt and Hoxc9expression dramatically decreased exposed to CAPs and/or O3in EAT and perirenal fat in the HF-group rats(p<0.001). In the ND-group, however, the down-regulation trends were also found but had no significant difference (p>0.05). No significant difference of the adiponectin concentration was found among the8groups both in EAT and peirenal fat supernatant (p>0.05). Significant increase of the threshold area%of macrophages was found in EAT and perirenal fat between HF-CAPs, HF-O3, and HF-CAPs/O3vs. ND-AIR (p<0.05). However, the increase of the threshold area%of macrophages was seen in EAT and perirenal fat between ND-CAPs, ND-O3, and ND-CAPs/O3vs. ND-AIR, but had no significant difference (p>0.05). As for the inflammatory genes expression, no elevation in IL-6was found in response to the short-term exposure to CAPS/O3. However, TNF-a, MCP-1and leptin expression dramatically up-regulated in response to the short-term exposure of the CAPs and or O3in EAT and perirenla fat in HF-group (p<0.0001). Interestingly, the HF-CAPs group revealed the highest TNF-a, MCP-1and leptin mRNA levels among the HF-CAPs, HF-O3and HF-CAPs/O3groups. Additionally, the mRNA levels of IL-10and adiponectin in EAT and perirenal fat were reduced in response to the short-term CAPs and or O3exposure both in ND and HF group (p<0.05). CAPs and or O3exposure resulted in the iNOS immunofluorescence signals increased in EAT and perirenal fat in HF-CAPs, HF-O3and HF-CAPs/O3vs. ND-AIR groups (p<0.05). Although the iNOS immunofluorescence revealed two folds elevation in HF-AIR vs. ND-AIR group, no significant difference was found (p>0.05). iNOS protein levels were elevated in HF-CAPs, HF-O3and HF-CAPS/O3vs. ND-AIR groups (p<0.05). In ND groups, however, no increases were seen in iNOS protein levels after exposed to the CAPs and/or O3(p>0.05). Short-term CAPs and or O3exposure did not induce marked decrease in mitochondria number in EAT and perirenal fat (p>0.05). However, it did result in a significant decline in the average area of mitochondria in ND-AIR vs. HF-CAPs, HF-O3and HF-CAPS/O3groups in EAT and perirenal fat (p<0.05). In the meanwhile, short-term CAPs and or O3exposure reduced mitochondria area in ND-AIR vs. ND-CAPs, ND-O3and ND-CAPS/O3groups in EAT and perirenal fat, although no significant difference was found (p>0.05).[Conclusions] EAT and perirenal fat depot are proved to be white adipose tissues. EAT, however, is markedly different from typical white fat and has some characteristic as brown adipose tissue. Short-term exposure of inhalational CAPs and/or O3leads to the white and brown adipose tissue specific genes significant down-regulation in EAT and perirenal fat, which implies that exposure of CAPs and/or O3interferes the adipose tissue metabolism in EAT and perirenal fat. Our data suggests that high-fructose chow triggers inflammation and oxidative stress in rats which can be dramatically exacerbated by short-term exposure to CAPs and/or O3. These findings imply that inflammation and oxidative stress in the EAT and perirenal fat may be one of the critical mechanisms of air pollution aggratating coronary atherosclerotic diseases and hypertension.
|
PDF Full Text Request