To observe and evaluate the effects of manipulation on knee osteoarthritis (KOA) using T2-mapping and magnetic resonance imaging (MRI)-based volume measurements.

To evaluate the efficacy of manipulation therapy in repairing thin-layer and thick-layer articular cartilage defects in rabbits.

Objective To investigate the changes in the expression of macrophage migration inhibitory factor (MIF) mRNA in a rat model of ventilator-induced lung injury.Methods Thirty adult male Sprague-Dawley rats,weighing 2β5-260 g,were randomly divided into 3 groups (n =10 each) using a random number table:control group (group C),small tidal volume (VT) mechanical ventilation group (group S) and large tidal volume mechanical ventilation group (group L).The animals were anesthetized with intraperitoneal ketamine 100 mg/kg,midazolam 0.2 mg/kg and atropine 1.0 mg/kg.The rats were tracheostomized and spontaneous breathing was maintained in group C,while the rats were tracheostomized and mechanically ventilated for 4 h in groups S and L.The tidal volume was 7 ml/kg (group S) or 40 ml/kg (group L),I ∶ E was 1 ∶ 1,RR was 80 bpm and FiO2 was 100％.At 4 h of spontaneous breathing or mechanical ventilation,broncho-alveolar lung lavage fluid (BALF) was collected for determination of the total protein concentration,white blood cell (WBC) counts and concentrations of MIF,IL-6 and IL-1β (by ELISA).Then the rats were sacrificed and the lungs removed for microscopic examination and for determination of wet to dry lung weight ratio (W/D ratio) and expression of MIF mRNA (by RT-PCR).Results Compared with C and S groups,WBC counts,concentrations of total protein,MIF,IL-6 and IL-1β in BALF,and W/D ratio and expression of MIF mRNA in lung tissues were significantly increased in group L (P ＜ 0.05).There was no significant difference in the indexes mentioned above between group C and group S (P ＞ 0.05).The pathological changes occurred in group L.Conclusion The up-regulation of MIF mRNA expression in lung tissues may be involved in the development of ventilator-induced lung injury in rats.

Objective To investigate the role of Toll-like receptor9 (TLR9)-myeloid differentiation factor 88 (MyD88) signal pathway in alveolar macrophages in ventilator-induced lung injury (VILI).Methods 30 adult male Sprague-Dawley (SD) rats were randomly assigned to three groups (with 10 rats in each group).Group A was the control group,with spontaneous respiration after tracheostomy.Rats in group B received mechanical ventilation for 4 hours with normal tidal volume (VT) 7 ml/kg after tracheostomy,and group C rats received mechanical ventilation with VT 40 ml/kg for 4 hours.After termination of ventilation,examination with transmission electron microscopy was performed to observe the ultrastructure changes in alveolar epithelial cell type Ⅱ (AEC Ⅱ) of the lung.Lung wet/dry ratios (W/D) and total protein concentration,the concentration of interleukins (IL-6 and IL-1 β) in bronchoalveolar lavage fluid (BALF) were determined.The protein and mRNA expressions of TLR9,MyD88 and nuclear factor-κB (NF-κB) in alveolar macrophages were assayed by Western Blot and real-time reverse transcription-polymerase chain reaction (RT-PCR).Results The ultrastructure of AEC Ⅱ in the group A and group B was almost normal,whereas the chromatin of the nuclei,the lamellar corpuscles in the cytoplasm,the cell membrane and the microvilli of the AEC Ⅱ in the group C showed injurious changes in various degrees.When the group C was compared with the group A and the group B,it was shown that the W/D ratios (5.54 ± 0.17 vs.4.58 ± 0.17,4.69 ± 0.16) and total protein concentration (g/L:6.33 ± 0.61 vs.0.45 ± 0.05,0.47 ± 0.04),IL-6 (μg/L:1.989 ± 0.103 vs.1.033 ± 0.061,1.010 ± 0.069) and IL-lβ (ng/L:2.79 ±0.25 vs.1.05 ±0.15,1.23 ±0.22) in BALF,the protein expressions of TLR9,MyD88 and NF-κB [TLR9 (A value):0.770 ±0.042 vs.0.300 ±0.027,0.310 ±0.037; MyD88 (A value):0.950 ±0.091 vs.0.560 ±0.082,0.580±0.084; NF-κB(A value):1.020 ±0.076 vs.0.740 ±0.052,0.700 ±0.076] in alveolar macrophages were all increased significantly,and all of which showed significant difference (P＜0.05 or P＜0.01).The mRNA levels of TLR9,MyD88 and NF-κB in alveolar macrophages in the group B were (1.13 ± 0.32),(1.18 ± 0.33),and (1.11 ± 0.22) folds of those of the group A,respectively,but there were no significant differences (all P＞0.05).While the mRNA levels of TLR9,MyD88 and NF-κB of alveolar macrophages in the group C were (8.66 ± 0.69),(6.41 ± 0.53) and (5.29 ± 0.71) folds of those of the group A,respectively,and all of them showed significant difference (all P＜0.01).Conclusion TLR9-MyD88 signaling in alveolar macrophages plays a role in pathogenesis of VILI.

Objective To evaluate the role of Toll-like receptor 2/nuclear factor-κB(TLR2/NF-κB)signaling pathway pretreatment in ventilator-induced lung injury(VILI). Methods Thirty male Sprague-Dawley(SD)rats were randomly divided into three groups by using random number scale,with 10 rats in each group. Group A:rats were given 200μL of TLR2 monoclonal antibodies(TLR2mAb,10μg/kg)by slow instillation through tracheal catheter, and then ventilated with a high tidal volume(VT)of 40 mL/kg. Group B:ventilated with a normal VT of 8 mL/kg. Group C:rats were tracheally instilled with 10 μg/kg of TLR2mAb devoid of biologic activity,and then ventilated with a high VT of 40 mL/kg. The rats were mechanically ventilated for 4 hours,the lung wet to dry weight ratio(W/D)was calculated. The changes in pathology and ultrastructure in lung tissue were observed with microscope. Enzyme linked immunosorbent assay(ELISA)was performed to determine the concentration of interleukins(IL-1β,IL-6)and tumor necrosis factor-α(TNF-α)in serum and brconchoalveolar lavage fluid(BALF). Real-time fluorescent quantitation reverse transcription-polymerase chain reaction(RT-PCR)was used to assess the mRNA expressions of TLR2, NF-κB and myeloid differentiation factor 88(MyD88)in lung tissue. Results No obvious pathological changes in lungs were found in group A and group B,and no obvious damages to ultra-microstructure were found in lung macrophages, typeⅠepithelial cell and typeⅡepithelial cell. In group C,pathological changes were observed,including pulmonary alveoli fusion,alveoli septum thickening,inflammatory cells infiltration,and damages to ultrastructure of lung macrophage,damage to cell membrane of typeⅠepithelial cells and typeⅡepithelial cells,vacuoles in cytoplasm, damage to organelle,and even pyknosis and perinuclear cistern thickening. Compared with group C,W/D ratio and mean concentration of inflammatory cytokines in serum and BALF showed a significant decrease in group A and B〔W/D ratio:1.151±0.026,1.128±0.048 vs. 1.403±0.062;concentration of IL-1βin serum(ng/L):37.05±5.61, 34.52±4.31 vs. 51.45±8.18;concentration of IL-6 in serum(ng/L):53.65±5.16,55.77±5.62 vs. 89.96±7.08;concentration of TNF-αin serum(ng/L):71.93±13.29,67.36±11.42 vs. 96.20±11.60;concentration of IL-1βin BALF(ng/L):56.48±6.16,54.44±7.26 vs. 99.77±8.41;concentration of IL-6 in BALF(ng/L):172.44±21.26, 163.47±18.70 vs. 216.22±23.90;concentration of TNF-α in BALF(ng/L):235.81±42.75,231.72±40.38 vs. 374.85±69.61,all P<0.01〕,but there were no significant differences between group A and group B(all P>0.05). The mRNA expressions of TLR2,MyD88,and NF-κB were significantly decreased in group A and group B compared with those in group C〔TLR2 mRNA(2-ΔΔCt):1.021±0.287,0.938±0.196 vs. 3.862±0.871;MyD88 mRNA (2-ΔΔCt):1.235±0.277,1.300±0.306 vs. 3.618±1.107;NF-κB mRNA(2-ΔΔCt):0.519±0.036,1.043±0.170 vs. 20.280±9.466,P<0.05 or P<0.01〕,but there was no significant difference among the parameters mentioned above between group A and B(all P>0.05). Conclusion To some extent,pre-intervention with TLR2mAb to block the TLR2/NF-κB signal pathway can inhibit the release of pro-inflammatory factors,and regulate the VILI.

Objective To investigate the role of Ras-related C3 botulinum toxin substrate 1/mitogen-activated protein kinase/extracellular signal-regulated kinase (Rac 1/MAPK/ERK) signal pathway in rats with ventilator induced lung injury (VILI) and its mechanism.Methods Thirty Sprague-Dawley (SD) rats were randomly divided into spontaneous respiration group,normal tidal volume (VT) group and high VT group with 10 rats in each group.The rats in spontaneous respiration group were kept their spontaneous breathing.The rats in normal VT group and high VT group were performed tracheal intubation after tracheostomy,and underwent mechanical ventilation on bilateral lungs with 6 mL/kg and 40 mL/kg VT respectively with maintenance anesthesia.After 4-hour ventilation,heart blood,bronchoalveolar lavage fluid (BALF) and lung tissues were harvested.The levels of interleukins (IL-1β,IL-6),tumor necrosis factor-α (TNF-α),myeloperoxidase (MPO) and macrophage inflammatory protein-2 (MIP-2) in serum and BALF were determined by enzyme linked immunosorbent assay (ELISA).Lung wet/dry radio (W/D) was determined.The lung tissues were stained with hematoxylin and eosin (HE),and pathological changes were observed,and pathological scores were evaluated.The ultra structure changes in type Ⅱ alveolar epithelial cells (AEC Ⅱ)were observed with transmission electron microscope.The positive expressions of phosphorylation of extracellular signal-regulated kinase (p-ERK) were determined by immunohistochemistry,and those of Racl and F-actin were determined by immunofluorescence.The mRNA expressions of ERK and Rac1 were determined by real-time fluorescent quantitation reverse transcription-polymerase chain reaction (RT-qPCR),and protein expressions of Rac-1,p-ERK and F-actin were determined by Western Blot.Results ① Compared with spontaneous breathing group,lung W/D in both mechanical ventilation groups was significantly increased,with more significant increase in the high VT group (6.64 ± 0.88 vs.1.79 ± 0.36,P ＜ 0.01).② There was no obvious pathological changes in the lung tissue and AEC Ⅱ of the spontaneously breathing group.In the normal VT group,there was slight edema and infiltration of inflammatory cells;AEC Ⅱ had less lamellar bodies and uniform distribution of the villi of the alveolar epithelium.In the high VT group,the edema of the lung tissue,the widening of the pulmonary septum,the alveolus congestion,the infiltration of inflammatory cells,and alveolar structure disorder were found;and AEC Ⅱ was irregular,the number of lamellar bodies in the plastids was decreased and was unevenly distributed.The pulmonary histopathological score in the high VT group was significantly higher than that in the spontaneous breathing group and the normal VT group (12.00 ± 2.00 vs.6.00 ± 1.51,8.50 ± 0.53,both P ＜ 0.01).③ Compared with spontaneous breathing group,IL-1β,IL-6,TNF-α,MPO,and MIP-2in serum and BALF in both mechanical ventilation groups were significantly increased,with more siguificant increase in the high VT group [serum IL-1 β (ng/L):104.2 ± 15.1 vs.20.3 ± 8.3,IL-6 (ng/L):46.6 ± 11.5 vs.22.7 ± 7.5,TNF-α (ng/L):39.4±6.5 vs.5.4± 1.9,MPO (ng/L):0.66±0.24 vs.0.06±0.03,MIP-2 (ng/L):109.2±25.8 vs.22.8±8.4;BALF IL-1 β (ng/L):121.5 ± 25.6 vs.24.0 ± 7.5,IL-6 (ng/L):136.7 ± 32.7 vs.31.4 ± 10.5,TNF-α (ng/L):98.0 ± 14.8vs.10.1 ±2.6,MPO (ng/L):0.80±0.31 vs.0.08±0.04,MIP-2 (ng/L):144.4±28.9 vs.41.2±20.7;all P ＜ 0.01].④ There were only a few p-ERK,Rac1 and F-actin positive expressions in the spontaneous breathing group.The positive expressions in normal VT group were increased.In high VT group,the positive expression of p-ERK was significantly increased;Rac1 and F-actin were mainly distributed in the cell membrane and cytoplasm respectively,the positive expressions were further enhanced.⑤ The gene expressions of ERK and Rac1,and protein expressions of p-ERK,Rac1 and F-actin in the high VT group were significantly higher than those in the spontaneous breathing group and normal VT group [ERK mRNA (2-△△Ct):8.23±2.83 vs.1,3.02± 1.38,p-ERK protein (gray value):1.15±0.36 vs.0.61 ±0.23,0.88±0.22;Rac1 mRNA (2-△△Ct):4.45 ±2.26 vs.1,1.22±0.39,Rac1 protein (gray value):0.91 ±0.16 vs.0.48±0.11,0.55 ± 0.10;F-actin protein (gray value):0.70± 0.09 vs.0.49 ± 0.08,0.55 ± 0.04;all P ＜ 0.01].Conclusion F-actin expression in lung tissue was up-regulated in rats with VILI,which resulted in reconstruction of AEC Ⅱ cyto-skeleton,and variation of cell membrane permeability through Rac 1 /MAPK/ERK sigualing pathway during VILI.

OBJECTIVE: To investigate the relationship between different tidal volume (VT) mechanical ventilation (MV) and autophagy and mitochondrial damage in rats. METHODS: A total of 120 clean-grade male Sprague-Dawley (SD) rats were divided into five groups (n = 24) by random number table method, and then given 0 (spontaneous breathing), 10, 20, 30, 40 mL/kg VT for MV. The rats in each group were subdivided into four subgroups of 1, 2, 3, and 4 hours according to ventilation time, with 6 rats in each subgroup. The lung tissue and bronchoalveolar lavage fluid (BALF) were harvested, and alveolar macrophages (AMs) and type II alveolar epithelial cells (AEC II) were cultured in vitro. The mRNA and protein expressions of autophagy-associated protein microtubule-associated protein 1 light chain 3B-II (LC3B-II) and autophagy-related genes Beclin1 and p62 were determined by reverse transcription-polymerase chain reaction (RT-PCR) or Western Blot. Lung autophagosome formation was observed under transmission electron microscope. The levels of adenosine triphosphate (ATP), reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) in lung tissue were determined for assessing mitochondrial damage. RESULTS: There were no significant differences in the mRNA and protein expressions of LC3B-II, p62 and Beclin1 at 1 hour after ventilation among the groups. With the prolonged ventilation time, the mRNA and protein expressions of LC3B-II, p62 and Beclin1 in MV groups were increased gradually, peaked at 2-3 hours, and they were increased significantly in 30 mL/kg VT group as compared with those in spontaneous respiration group with statistical significances [ventilation for 2 hours: LC3B-II mRNA (2^-ΔΔCt) was 2.44±0.24 vs. 1.12±0.04, LC3B-II/LC3B-I was 1.42±0.16 vs. 0.57±0.03, p62 mRNA (2^-ΔΔCt) was 2.96±0.14 vs. 1.14±0.02, Beclin1 mRNA (2^-ΔΔCt) was 2.80±0.13 vs. 1.14±0.02; ventilation for 3 hours: p62/β-actin was 1.14±0.15 vs. 0.55±0.04, Beclin1/β-actin was 1.27±0.06 vs. 0.87±0.04, all P < 0.05]. Autophagosomes and autolysosomes were found in AEC II after ventilation for 2 hours at 30 mL/kg VT by transmission electron microscopy, but not in AEC I. Compared with spontaneous breathing group, ATP synthesis in AMs was significantly decreased at 2 hours of ventilation in 30 mL/kg VT group (A value: 0.82±0.05 vs. 1.00±0.00, P < 0.05), ROS accumulate in AMs and AEC II were significantly increased [ROS in AMs: (33.83±4.00)% vs. (6.90±0.62)%, ROS in AEC II: (80.68±0.90)% vs. (2.16±0.19)%, both P < 0.05]. With the increase in VT and the prolongation of ventilation time, ATP and ROS levels in AMs and AEC II were gradually decreased, the ATP (A value) in AMs at 4 hours of ventilation in 40 mL/kg VT group was 0.41±0.05, the ROS in AMs was (12.95±0.88)%, and the ROS in AEC II was (40.43±2.29)%. With the increase in VT and the prolongation of ventilation time, MMP levels were gradually increased, the MMP (green/red fluorescence intensity ratio) in AMs at 2 hours of ventilation in 30 mL/kg VT group was 1.11±0.17, the MMP in AEC II was 0.96±0.04, and the MMP (green/red fluorescence intensity ratio) at 4 hours of ventilation in 40 mL/kg VT group was 0.51±0.07 and 0.49±0.06, respectively. CONCLUSIONS The MV with high VT could induce autophagy activation and mitochondrial damage in lung tissue of rats, and the longer the ventilation time, the more obvious autophagy in the lung.
Animals ; Autophagy/physiology* ; Male ; Mitochondria/pathology* ; Rats ; Rats, Sprague-Dawley ; Respiration, Artificial/adverse effects* ; Tidal Volume ; Time Factors ; Ventilator-Induced Lung Injury

Objective:To investigate the effects of three monomer components stilbene glycoside, emodin, catechin of Polygonum multiflorum on damages of liver tissue and cell.Methods:A total of 48 rats were randomly divided into four groups of stilbene glycoside, emodin, catechin-and normal saline(control)-treated groups(n=12, each). Rats were gavaged with the same dose of 1 g/kg for stilbene glycoside, emodin, catechin groups and normal saline for control group for 28 days.During the administration, the general state of rat was observed.After the last administration, serum biochemical indexes related to liver function were detected.Pathological morphological changes of liver tissue were observed by hatmatoxylin-Eosin(HE)staining.The expression levels of apoptosis-related proteins in liver tissue were determined by Western blot.Cells of human normal liver cell line LO2 divided into the stilbene glycoside-, emodin-, catechin-treated cells groups were cultured with 7 different concentrations of interfering agents for 24 h and 48 h respectively, and cultured with normal saline in the control group for the same time.Cell proliferation was observed using the cholecystokinin octapeptide(CCK8), and the mRNA expressions of apoptosis-related factors were detected using PCR.Results:After 28 days of feeding, there was no significant difference in body weight and food intake among the four groups( P>0.05). Pathological liver damage and abnormal liver biochemical indexes were observed in rat liver tissues in the emodin and catechin groups( P<0.05). Compared with the control group, the expression levels of anti-apoptotic proteins Bcl-2 were decreased(0.34±0.03, 0.41±0.07 vs.0.45±0.04, P<0.05), the expression levels of apoptotic proteins Caspase-3 and Bax were increased(0.76±0.03, 0.27±0.06 vs.0.03±0.00; 0.44±0.03, 0.15±0.04 vs.0.02±0.00, P<0.01), and those in the stilbene glycoside group were normal.Compared with the control group, emodin and catechin-treated cell groups showed the concentration-and time-dependent proliferation inhibition in LO2 normal hepatocytes( P<0.05)after treatment.And the mRNA expression of hepatocyte apoptosis factors Bax and Caspase-3 were increased(1.74±0.05, 1.29±0.01 vs.0.89±0.12, 1.21±0.07, 1.25±0.01 vs.0.97±0.07, P<0.01), and that of anti-apoptotic proteins Bcl-2 was decreased(0.06±0.06, 0.56±0.11 vs.1.39±0.18, P<0.01). Compared with the control group, the survival rate had no significant difference in the stilbene glycoside treated-cell group( P>0.05), while its mRNA expression of hepatocyte apoptosis factors was reduced( P<0.05). Conclusions:No obvious liver damage is found in rats treated with the stilbene glycoside of Polygonum multiflorum, but the emodin and catechin cause damages of liver tissue and cell in vivo and in vitro.

Objective: To investigate the role and mechanism of Ly6C^high monocyte in mice with ventilator-induced lung injury (VILI). Methods: Forty-eight healthy male SPF C57BL/6 mice were divided into spontaneous breathing group (n = 8), normal tidal volume (VT) group (VT was 8 mL/kg, n = 8), and high VT group (VT was 20 mL/kg, n = 32). The mice in the high VT group were subdivided into 1, 2, 3 and 4 hours subgroups, with 8 mice in each subgroup. All mice underwent direct tracheal intubation, those in the spontaneous breathing group maintained spontaneous breathing, and those in the normal VT group and high VT group were mechanically ventilated with different VT. After ventilation for 4 hours, bronchoalveolar lavage fluid (BALF) was collected to determine total protein, and the levels of inflammatory factors including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were determined by enzyme-linked immune sorbent assay (ELISA). The lung tissues were harvested to determine the wet/dry (W/D) ratio, and lung tissue injury was assessed in terms of lung histopathologic examination after hematoxylin-eosin (HE) staining under the light microscope. The protein expressions of monocyte chemotactic protein-1 (MCP-1) and CC-chemokine receptor 2 (CCR2) in lung tissues were determined by Western Blot. Flow cytometry was used to detect the proportion of Ly6C^high monocyte in lung tissue. Results: The histopathology of lung tissue structures was normal in the spontaneous breathing group and the normal VT group. Inflammatory reaction began to appear at 2 hours of high VT ventilation, and inflammatory reaction was gradually aggravated with the time extension. Compared with the spontaneous breathing group, the total protein, TNF-α, and IL-1β levels in BALF, the lung W/D ratio and MCP-1 expression were increased from 2 hours of high VT ventilation [total protein in BALF (g/L): 1.05±0.13 vs. 0.58±0.11, TNF-α in BALF (ng/L): 116.86±16.14 vs. 38.27±8.00, IL-1β in BALF (ng/L): 178.98±10.41 vs. 117.56±23.40, lung W/D ratio: 5.76±0.27 vs. 4.98±0.39, MCP-1/GAPDH: 0.87±0.19 vs. 0.29±0.12, all P < 0.05], and CCR2 expression and the proportion of Ly6C^high monocyte was significantly increased from 3 hours of high VT ventilation [CCR2/GAPDH: 0.84±0.19 vs. 0.24±0.11, Ly6C^high monocyte proportion: (9.01±2.47)% vs. (1.06±0.35)%, both P < 0.05], and they all showed an increased tendency with the time extension. There was no significant difference in the parameters mentioned above among the spontaneous breathing group, normal VT group and high VT ventilation 1-hour group. Conclusion Ly6C^high monocytes are involved in VILI, which aggravate VILI by activating the MCP-1/CCR2 axis.

Objective:To investigate the protective effect and mechanism of dexamethasone in lung ischemia/reperfusion injury (LIRI) rats.Methods:① Part one experiment: 24 Sprague-Dawley (SD) rats were divided into four groups according to the random number method ( n = 6): standard ventilation group (N group), normal saline group (NS group), LIRI group, and dexamethasone+LIRI group (DEX group). The rat model of LIRI was established by clamping the left pulmonary hilum for 1 hour and reperfusing it for 2 hours. The DEX group was given dexamethasone 3 mg/kg 5 minutes before reperfusion, and NS group was injected with normal saline. Group N did not receive any treatment. The left lung tissue of the rats in each group were taken alive 2 hours after reperfusion. The lung tissue was harvested for lung wet/dry mass ratio (W/D) measurement. Hematoxylin-eosin (HE) staining and electron microscopy was used to observe the pathological changes of lung tissue and to assess the degree of injury. Ultrastructural changes of lung tissue were observed under electron microscope. The levels of tumor necrosis factor-α (TNF-α), interleukin (IL-1β, IL-6) in lung tissue were detected by enzyme linked immunosorbent assay (ELISA). The expressions of phosphorylated protein kinase B (p-AKT) was detected by Western Blot. ② Part two experiment: intervention with phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway inhibitor LY294002 to further explore the mechanism of dexamethasone in reducing lung injury induced by LIRI. Twenty-four SD rats were divided into four groups according to the random number method ( n = 6): N group, LIRI group, DEX group, and dexamethasone+LY294002+LIRI group (LY group). All the groups except the LY group were treated with membrane and intervention according to part one experiment. The LY group was injected with LY294002 0.3 mg/kg after injection of dexamethasone. The expressions of M1 macrophage polarization markers CD11c, CD16, and M2 macrophage polarization markers CD206, Arg1 were detected by immunohistochemistry. Results:① Part one experiment: compared with N group, the morphological and ultrastructural changes of lung tissue in the LIRI group were significantly changed, lung injury score, lung W/D ratio and TNF-α, IL-1β, IL-6 levels were significantly increased, and p-AKT expression was significantly decreased. Compared with the LIRI group, the morphological and ultrastructural changes of the lung tissue in the DEX group were significantly improved, and the lung injury score was reduced (5.00±0.89 vs. 8.83±0.75), lung W/D ratio and TNF-α, IL-1β, IL-6 levels were significantly decreased [lung W/D ratio: 6.25±0.56 vs. 8.27±0.72, TNF-α(ng/L): 93.28±16.42 vs. 205.90±25.30, IL-1β(ng/L): 130.10±10.81 vs. 209.10±19.20, IL-6 (ng/L): 195.80±21.17 vs. 310.50±20.77], p-AKT expression was significantly increased [p-AKT/AKT: (57.58±8.80)% vs. (36.62±9.25)%], and the differences were statistically significant (all P < 0.05). There was no significant difference in each index between NS group and N group. ② Part two experiment: compared with the N group, the expression of macrophage polarization markers CD11c, CD16, CD206 and Arg1 in the LIRI group were significantly increased. Compared with the LIRI group, the expressions of CD11c and CD16 in the lung tissue of the DEX group were significantly decreased, and the expressions of CD206 and Arg1 were significantly increased. The intervention of PI3K/AKT signaling pathway inhibitor LY294002 significantly blocked the effect of dexamethasone on LIRI-mediated macrophage polarization (CD11c immunohistochemical score: 7.20±0.36 vs. 5.00±0.34, CD16 immunohistochemical score: 8.20±0.48 vs. 7.40±0.64, CD206 immunohistochemical score: 5.80±0.59 vs. 7.40±0.28, Arg1 immunohistochemical score: 7.20±0.72 vs. 8.80±0.48, all P < 0.05). Conclusions:Dexamethasone pretreatment can alleviate the intrapulmonary inflammatory response and lung injury caused by LIRI in rats. The mechanism of action is related to the polarization direction of pulmonary macrophagesvia activation of the PI3K/AKT pathway by dexamethasone.