The Effects And Mechanisms Of Short-term Exposure To PM_2.5 On Coagulation In Rats

Objective: Epidemiological studies demonstrate that exposure to fineparticulate matter （PM） is associated with an increased risk for ischemiccardiovascular events including acute myocardial infarction and ischemicstroke. Air pollution definitely increases rates of morbidity and mortalitybecause of atherothrombotic events, causes more frequent hospitalizations. Inaddition, exposure to particulate matter is associated with an increased riskfor venous thromboembolism. The mechanisms have not been elucidated.While developing a model of PM_2.5exposure in rats, we investigated theeffects of PM_2.5on coagulation by detecting PT、APTT、FIB in plasma. Weinvestigated the effects of PM_2.5on pulmonary inflammation by determing thetotal and differential cell counts and concentrations of proinflammatorycytokine interleukin IL-6,TNF-a in BALF. In order to investigat the effects ofPM_2.5on oxidative stress and endothelial dysfunction, we detected thecontents of MDA and VWF by ELISA and the protein levels of AT₁in lung ofrats by Western blot. We investigate the effect of PM_2.5on coagulation in ratsand discuss the mechanism from pulmonary inflammation and endothelialdysfunction.Methods:24healthy Sprague-Dawley（SD） female rats of clean gradewere divided into four groups randomly.â‘ c ontrolgroup;â‘¡3.75mg/kgPM_2.5group;â‘¢7.5mg/kgPM_2.5group;â‘£15mg/kgPM_2.5group.The control groupwere injected of normal saline （1.5ml/1kg） into trachea, the group PM_2.5received3.75mg/kg,7.5mg/kg,15mg/kg of PM_2.5suspended in saline（1.5ml/kg）.The rats were sacrificed by deep anesthesia on24hours afteradministration. We collected the plasma to detected the PT,APTT,FIB. Thelower lobes of right lungs were cut into sections and stained with hematoxylin–eosin （H–E） to be observed the pathomorphism changes of lung tissue. Bronchoalveolar lavage fluid（BALF）was collected by cannulating the tracheaand lavaging the left lungs. We detected the total and differential cell counts inBALF. The levels of IL-6and TNF-a in BALF were determined by the methodof enzyme linked immunosorbent assay（ELISA）. The contents of VWF inSerum and MDA in the lung were determined by the method of enzymelinked immunosorbent assay（ELISA）.Western blot was performed to detectthe protein levels of AT₁receptors in the lung of rats. Statistics work was donewith SPSS13.0statistical software.Results:1Changes in PT,APTT and FIB in the plasmaThere were no statistical differences in PT beweent3.75mg/kg PM_2.5group and control group（P>0.05）. Compared with rats in control group and3.75mg/kg PM_2.5group, rats in7.5mg/kg PM_2.5group and15mg/kg PM_2.5group showed a reduction in PT（P<0.05）. Compared with rats in7.5mg/kgPM_2.5group, mice in15mg/kg PM_2.5group showed a reduction inPT（P<0.05）.There were no statistical differences in APTT in the plasma beweent3.75mg/kg PM_2.5group and the control group（P>0.05）. Compared with rats incontrol group and3.75mg/kg PM_2.5group, rats in7.5mg/kg PM_2.5group and15mg/kg PM_2.5group showed a reduction in APTT（P<0.05）. There were nostatistical significance in APTT between the7.5mg/kg PM_2.5group and15mg/kg PM_2.5group （P＞0.05）.There were no statistical differences in FIB in all groups（P＞0.05）.2The results of pulmonary pathologyCompared with the control group, alveolar septum was slightlythicker,and inflammatory cell （Mainly macrophages and neutrophils）infiltrated in the pulmonary interstitial and alveolar in all of PM_2.5group.inflammatory infiltration in15mg/kg PM_2.5group was more severitier thanthat in7.5mg/kg PM_2.5group. With the increase of dose of PM_2.5, the degree ofinflammation of lung tissue was more severitier. 3The total cell count of BALF and cell classificationIn comparison with the rats in control group, the rats exposed to differentconcentration PM_2.5showed significant increases in the numbers of total cellsand percentage of neutrophils （P<0.05）. The total cell numbers and percentageof neutrophils in BALF were significantly increased with the increase of doseof PM_2.5（P<0.05）.4The changes of concentration of IL-6and TNF-α in the BALFThe concentration of IL-6in BALF were significantly elevated in7.5mg/kg PM_2.5group and15mg/kg PM_2.5group compared with that of thecontrol group and3.75mg/kgPM_2.5group （P<0.05）. Compared with that of7.5mg/kg PM_2.5group, the concentration of IL-6in15mg/kg PM_2.5groupwere significantly increased （P<0.05）. There were no statistical significance inthe concentration of IL-6in BALF between the3.75mg/kg PM_2.5group andcontrol group （P＞0.05）.The concentration of TNF-α in BALF were significantly elevated in7.5mg/kg PM_2.5group and15mg/kg PM_2.5group compared with that of thecontrol group and3.75mg/kgPM_2.5group （P<0.05）. There were no statisticalsignificance in the concentration of TNF-α in BALF between the3.75mg/kgPM_2.5group and control group （P＞0.05）.There were no statistical differencesin the concentration of TNF-α in BALF between7.5mg/kg PM_2.5group and15mg/kg PM_2.5group（P>0.05）.5The protein levels of AT₁receptors in lungThe protein level of AT₁receptors in the lungs in7.5mg/kg PM_2.5groupand15mg/kg PM_2.5group was significantly higher than that in control groupand3.75mg/kg PM_2.5group（P<0.05）. There were no statistical significance inthe protein level of AT₁receptors in lung between3.75mg/kg PM_2.5group andthe control group （P＞0.05）. The protein level of AT₁receptors in the lung in15mg/kg PM_2.5group was significantly higher than that in7.5mg/kgPM_2.5group（P<0.05）.6The changes of contents of Malondialdehyde （MDA） in the lungThe contents of MDA in the lung in7.5mg/kg PM_2.5group and15mg/kgPM_2.5group was significantly higher than that in control group and3.75mg/kg PM_2.5group（P<0.05）. There were no statistical significance in the contents ofMDA in the lung between3.75mg/kg PM_2.5group and the control group （P＞0.05）. The contents of MDA in the lung in15mg/kg PM_2.5group wassignificantly higher than that in7.5mg/kgPM_2.5group（P<0.05）.7The changes of contents of Von Willebrand factor （VWF）in the serumThe contents of VWF in the serum in7.5mg/kg PM_2.5group and15mg/kgPM_2.5group was significantly higher than that in control group and3.75mg/kgPM_2.5group（P<0.05）. There were no statistical significance in the contents ofVWF in the serum between3.75mg/kg PM_2.5group and the control group （P＞0.05）. The contents of VWF in the serum in15mg/kg PM_2.5group wassignificantly higher than that in7.5mg/kgPM_2.5group（P<0.05）.Conclusion:1Short-term exposure to PM_2.5could result in a reduction in PT andAPTT and induce hypercoagulability.2Exposure to PM_2.5could lead to lung inflammation and release of IL-6and TNF-a, which could enhance the vascular AT₁receptor expression.Overexpression of AT₁receptors leads to increased oxidative stress and thedevelopment of endothelial dysfunction, which in turn inducehypercoagulability.