Effect of azithromycin on airway inflammation and airway mucus hypersecretion in rats with chronic obstructive pulmonary disease

AIM: To observe the effect of azithromycin on the rats with chronic obstructive pulmonary disease (COPD), and to explore the underlying mechanism about the airway inflammation and mucus hypersecretion. METHODS: Male SD rats were randomly divided into normal control group, COPD model group, azithromycin treatment group. The COPD model was established by the method of cigarette smoking combined with intratracheal injection of LPS. Pathological changes of the bronchi and lung tissues of the rats were observed with HE staining. Pulmonary ventilation function in the rats was detected with pulmonary function instrument. The levels of IL-8, IL-17 and TNF-α in bronchoalveolar lavage fluid (BALF) were measured by ELISA. The expression of MUC5ac and TLR4 at mRNA and protein levels in bronchi and lung tissues was determined by real-time PCR and Western blot.RESULTS: HE staining showed that the changes of bronchi and lung tissues in model group were consistent with typical pathological manifestations of COPD. Compared with model group, these changes were alleviated in treatment group. The pulmonary functions in model group were significantly decreased compared with control group. The levels of IL-8, IL-17 and TNF-α in the BALF in model group were significantly increased compared with control group (P <0.05). The expression of MUC5ac and TLR4 at mRNA and protein levels in model group was significantly higher than that in control group (P <0.05). Compared with model group, the degree of the descent in pulmonary function in treatment group was significantly lessened. Compared with model group, the levels of IL-8, IL-17 and TNF-α in treatment group were significantly inhibited (P <0.05). Furthermore, the expression of MUC5ac and TLR4 at mRNA and protein levels in treatment group was significantly lower than that in model group (P <0.05). CONCLUSION: Azithromycin decreases the levels of IL-8, IL-17 and TNF-α in the BALF of COPD model rats, inhibits the protein expression of MUC5ac and TLR4 in the lung tissues, thus playing a preventive and therapeutic role to reduce airway inflammation and airway mucus hypersecretion.     

Relationship between airway inflammation and bronchial hyperreactivity in rats and the effect of theophylline

AIM: To determine the relationship between antigen-induced airway inflammation characterized by pulmonary eosinophilia and bronchial hyperreactivity in rats, and to evaluate the effect of theophylline at different doses. METHODS: In ovalbumin (OA)-sensitized rats, bronchiole wall area, eosinophils around bronchi, and the responses to methacholine (MCh) aerosol were measured after 1% OA aerosol challenge with computer-assisted techniques. RESULTS: OA challenge caused both inflammation and airway hyperreactivity, and there was a significantly positive correlation between them. Oral theophylline (1-12.5 mg/kg, bid for 7 days) attenuated antigen-induced inflammation (swelling of bronchiole walls and pulmonary eosinophilia) and bronchial hyperreactivity. CONCLUSION: These findings confirm that bronchial hyperreactivity positively correlates to airway inflammation in the rat, and suggest that theophylline at relatively lower doses has anti-inflammatory effect in airway allergic reaction.     

Pathological features of airway inflammation in eosinophilic bronchitis

AIM: To explore the pathological features of airway inflammation in patients with eosinophilic bronchitis (EB) and compared to those with cough variant asthma (CVA). METHODS: Flexible fibre optic bronchoscopy was performed in 11 patients with EB, 10 with CVA, 14 with bronchial asthma and 10 normal controls. The mean thickness of the basement membrane was measured by light microscopy. Using immunohistochemical and special staining, the localization and density of inflammatory cells (eosinophils, mast cells, T lymphocytes) were detected in bronchial submucosa in EB and CVA patients. RESULTS: The mean thickness of the basement membrane was significantly increased in the subjects with EB ［2.92 μm (2.10-6.50 μm)］, CVA ［5.64 μm (3.23-8.48 μm)］ and bronchial asthma ［9.08 μm (6.61-11.99 μm)］ rather than that in the normal controls ［2.08 μm (1.62-3.40 μm)］. There were also significant differences among the three groups. The number of mast cells and eosinophils in the bronchial submucosal from subjects with EB ［75 cells/mm2 (35-112 cells/mm2), 7 cells/mm2 (0-31 cells/mm2)］ was substantially decreased than those in subjects with CVA ［148 cells/mm2 (34-200 cells/mm2), 114 cells/mm2 (1-768 cells/mm2); P<0.05］. There was no significantly difference in T lymphocyte counts between the EB and CVA. CONCLUSIONS: EB is an inflammatory disorder of the airways with the characteristics of various inflammatory cell (eosinophils, mast cells and T lymphocytes) infiltration. The mean thickness of the basement membrane is less severe than that in CVA and bronchial asthma and the level of infiltration of inflammatory cells is less than that in CVA, which may be one of the reasons that airway hyperresponsiveness is rarely seen in EB.     

Effect of ligustrazine on pulmonary arterial pressure and pulmonary arterial wall collagen of chronic hypoxic hypercapnic rats

AIM:To study the effect of ligustrazine on pulmonary hypertensive rats induced by hypoxic hypercapnia. METHODS:Thirty rats were randomly divided into three groups:control group(A),hypoxic hypercapnic group(B), hypoxic hypercapnia+ligustrazine(lig.) group(C). RESULTS: (1) Mean pulmonary arterial pressure(mPAP)of group B was significantly higher than that of group A and mPAP of group C was significantly lower than that of group B(P＜0.01),differences of mean carotid pressure(mCAP) were not significant among three groups (P＞0.05); (2)Electron microscopy and immunohistochemistry showed ligustrazine could inhibit the diposition of collagenous fiber(collagen typeⅠ)in pulmonary arterioles induced by hypoxic hypercapnia; (3) Plasma endothelin level of group C was significantly lower than that of group B (P＜0.01), serum (NO ₂^-/NO₃^-) of group C was significantly higher than that of group B (P＜0.01). CONCLUSION:Ligustrazine can inhibit pulmonary hypertension and the diposition of collagen type Ⅰ in pulmonary arterial wall induced by hypoxic hypercapnia.     

Relationship between calcium-activated chloride channels and mucus overproduction,allergic airway inflammation in asthma

Calcium-activated chloride channels play important roles in the pathological processes in asthma with mucus overproduction and a series of airway inflammation. The function of calcium-activated chloride channels depends on their structure and characterization. The members of chloride channels, calcium activated (CLCA) family of proteins and in particular murine mCLCA3 (alias Gob-5) are possible initial factors of mucus overproduction in asthma. Regulation of mCLCA3 is relevant with cytokines secreted by Th2 cells. Over-expression of Gob-5 and hCLCA1 increase the translation of MUC5AC gene, which upregulates the secretion of goblet cells. Further study on the function and structure of calcium activated chloride channels may provide new evidence for understanding the pathogenesis of asthma.     

Antagonistic effects of aminophylline on airway inflammation and oxidative lung tissue damage in chronic hypoxic rats

AIM: To investigate the effects of chronic hypoxia and antagonistic effects of aminophylline on airway inflammation and oxidative lung damage in rats. METHODS: Thirty-four male Wistar rats were randomly divided into three groups: normal control group (n=10); hypoxia group (n=12); aminophlline-treated group (n=12). The last two groups were both exposed to hypoxia 7 hours per day for 21 days. The third group was treated with aminophlline (100 mg·kg-1·d-1) before exposed to hypoxia. The level of tumor necrosis factor (TNF) -α, interleukin (IL)-10, lipid peroxide (LPO) and the activity of superoxide dismutase (SOD) were determined in blood and homogenates of lung tissue. RESULTS: Compared to the control group, the levels of TNF-α, IL-10 and LPO were significantly increased (P<0.01), the activity of SOD was significantly decreased (P<0.01) both in blood and homogenate of lung tissue. The ratio of TNF-α and IL-10 was significantly increased (P<0.01) in homogenate of lung tissue in hypoxia group. Compared to the hypoxia group, the levels of TNF-α, LPO and the ratio of TNF-α and IL-10 were significantly decreased (P<0.01) in blood and homogenate of lung tissue in aminophylline treated group, while the level of IL-10 and activity of SOD was significantly increased (P<0.05, P<0.01, respectively). CONCLUSIONS: Chronic hypoxia induces airway inflammation. Aminophylline produces anti-inflammatory effects on airway and anti-oxidantive effects on lung.     

Role of transforming growth factor-β in the airway inflammation and remodeling in asthma

Transforming growth factor-β (TGF-β) was reported to be increased in asthma in some studies. Accumulation of TGF-β in airway promotes smooth muscle cell mitogenesis and hyperplasia, and induces fibroblast and myofibroblast and smooth muscle proliferation as well as increase in protein synthesis in connective tissue (such as collagen deposition on the reticular basement membrane). The autocrine induction of collagen expression by smooth muscle may contribute to the thickening of the reticular basement membrane, irreversible fibrosis and remodeling seen in the airways in some asthmatics. TGF-β is considered to be a major fibrogenic cytokine. It can increase smooth muscle mass and lead to severe bronchial obstruction in an asthma attack.     

Effect of diltiazem on pulmonary arterial pressure and ceNOS mRNA expression in pulmonary arteries in chronic hypoxic hypercapnic rats

AIM: To investigate the effect of diltiazem on mean pulmonary arterial pressure (mPAP) and nitric oxide synthase (NOS) in arterioles in chronic hypoxic hypercapnic rats. METHODS: Twenty-four rats were randomly divided into three groups: control group (A), hypoxic hypercapnic group (B), hypoxic hypercapnia+ diltiazem group (C), constitutive endothelial NOS (ceNOS) were observed in arterioles of rats using the technique of immunohistochemistry, ceNOS mRNA were observed by the technique of in situ hybridization. RESULTS: (1) mPAP was significantly higher in rats of B group than that of A and C group(P<0.01). Differences of mCAP were not significant between A group and B groups (P>0.05), but mCAP was lower in rats of C group than that in B group. (2) Light microscopy showed WA/TA (vessel wall area/total area) was significantly lower in rats of C group than that of B group (P<0.01), electron microscopy showed that diltiazem inhibited the proliferation of smooth muscle cells and collageous fibers of pulmonary arterioles in chronic hypoxic hypercapnic rats. (3) Immunohistochemistry showed the average value of integral light density (LD) of ceNOS in pulmonary arterioles was significantly higher in rats of C group than that of B group (P<0.01), in situ hybridization showed LD of ceNOS mRNA in pulmonary arterioles was significantly higher in rats of C group than that of B group (P<0.01). CONCLUSION: Diltiazem inhibited pulmonary hypertension, the proliferation of smooth muscle cells and collagenous fibers of pulmonary arterioles in chronic hypoxic hypercapnic rats by incresing the expression of ceNOS in pulmonary arterioles.     

Effect of hydroxylamine on pulmonary arterial hypertension induced by chronic hypoxic hypercapnia in rats

AIM: To explore the effects of hydroxylamine on the pulmonary arterial pressure in chronic hypoxic hypercapnic rats. METHODS: Twenty-four male Sprague-Dawley rats were randomly divided into 3 groups (8 rats in each group): the normal control group (NC), hypoxic hypercapnia+normal saline group (NS), hypoxic hypercapnia+hydroxylamine group (HA). The animals in NS and HA groups were kept in the O₂ (9%-11%) and CO₂ (5%-6%) cabin, 8 h a day and 6 days a week for 4 weeks. Before entering the cabin, the rats in HA group were administered with 1 mL hydroxylamine (12.5 mg/kg) by intraperitoneal injection, while the rats in NS group were given intraperitoneal injection of 1 mL saline solution. The mean pulmonary arterial pressure (mPAP) was measured by external jugular vein cannulation. The heart was removed, and the right ventricle (RV) and the left ventricle plus the septum (LV+S) were dissected. The ratio of the wet weight of the RV to that of the LV+S was calculated. The changes of the pulmonary vascular construction were observed under optical microscope. The concentration of H₂S in the plasma was measured with a spectrometer. The expression of cystathionine-γ-lyase (CSE) in the pulmonary arterioles and bronchi was measured by immunohistochemistry and RT-PCR. RESULTS: The values of mPAP, RV/(LV+S),vessel wall area/total area (WA/TA) and media thickness of pulmonary arterioles (PAMT) in NS group and HA group were significantly higher than those in NC group (P<0.05). The level of H₂S in the plasma, the content of CSE protein and the expression of CSE mRNA in NC group were significantly lower than those in NS group (P<0.05). The values of mPAP, RV/(LV+S), WA/TA and PAMT in HA group were significantly lower than those in NS group (P<0.05). The level of H₂S in the plasma, the content of CSE protein and the expression of CSE mRNA in HA group were significantly higher than those in NS group (P<0.05). CONCLUSION: Hydroxylamine may decrease the pulmonary arterial hypertension induced by chronic hypoxic hypercapnia in rats by increasing the level of H₂S in the plasma, the content of CSE protein and the mRNA expression of CSE, thus improving the pulmonary vascular structural remodeling.     

Effects of miR-124 over-expression on right ventricular remodeling in rats with pulmonary hypertension

AIM: To investigate the effect of microRNA-124 (miR-124) over-expression mediated by adeno-associated virus (AAV) on right ventricular remodeling in rats with pulmonary arterial hypertension (PAH) induced by monocrotaline (MCT). METHODS: Male SD rats (n=32) were randomly divided into 4 groups:normal control (control) group, MCT+normal saline (NS) group, MCT+AAV-GFP (MCT+GFP) group and MCT+AAV-miR-124 (MCT+miR-124) group. The rats in the latter 3 groups were instilled slowly with 100 μL NS, AAV-GFP and AAV-miR-124 by orotracheal instillation after anesthesia, respectively. Three weeks later, MCT (60 mg/kg) was intraperitoneally injected to establish the PAH model. Right ventricular systolic blood pressure (RVSP) and mean arterial pressure of the rats were measured, and right ventricular hypertrophy index (RVHI) and right ventricular weight index (RVWI) were calculated. The pathological sections of the right heart were stained with Sirius red, and the pathological changes of myocardium were observed under a microscope. The expression of miR-124 in the lung tissues was detected by RT-qPCR. The protein levels of transforming growth factor-β₁(TGF-β₁) and p-Smad2 in right heart tissues were determined by Western blot. RESULTS: Compared with control group, RVSP, RVHI, RVWI and the protein levels of TGF-β₁ and p-Smad2 in MCT+NS group and MCT+GFP group were significantly increased (P<0.05), the right ventricular myocytes were significantly enlarged, and collagen deposition was significantly increased. However, compared with MCT+GFP group, RVSP, RVHI, RVWI and the protein levels of TGF-β₁ and p-Smad2 in MCT+miR-124 group were significantly decreased (P<0.05), the degree of right ventricular myocyte hypertrophy was significantly reduced, and collagen deposition was significantly reduced. CONCLUSION: Over-expression of miR-124 obviously reduces RVSP of rats induced by MCT and relieves myocardial remodeling, which may be related to the down-regulation of TGF-β₁ and p-Smad2.     

Chronic exposure to house dust mite induces airway remodeling related to Th1 inflammation in mice

AIM: To investigate the inflammatory characteristics in the airway of mice with chronic exposure to dust mite. METHODS: The α-SMA-Cre/R26R transgenic reporter mice were intranasally exposed to dust mite extract for 60 d (DME group), and then subjected to the measurement of lung resistance. The performance of bronchoalveolar lavage, pathological changes of the lung tissues and splenocytes isolation 24 h after the last challenge were observed. The protein extracts from the lungs were subjected to the detection of α-smooth muscle actin (α-SMA) by Western blotting. The supernatants of the lung homogenate were collected for testing the levels of interleukin-4 (IL-4) and interferon-γ (IFN-γ) with enzyme-linked immunosorbent assay. CD4⁺ T-cell subsets of the splenocytes were analyzed by flow cytometry.RESULTS: The mice chronically exposed to dust mite extract demonstrated severe airway hyperresponsiveness. The pulmonary pathological sections with HE staining manifested strong evidence of airway remodeling in DME group, corresponding to an enhanced X-gal staining that is related to α-SMA activation in the subepithelial basement membrane of bronchia. Total cell and lymphocyte counts were increased in the lungs of DME group compared to control group. No difference was found in eosinophil count of mice between DME and control groups. There was an elevated level of IFN-γ in the lungs of DME challenged mice coordinated with an increased proportion of IFN-γ-producing CD4⁺ T cells in the splenocytes.CONCLUSION: Chronic exposure to dust mite in the mice induces Th1-dominant inflammation with an airway hyperresponsiveness and the development of airway remodeling.     

The relationship between cough response and airway inflammation in guinea pigs sensitized and challenged with ovalbumin

AIM: To investigate the effects of intensity of eosinophilic airway inflammation on cough response in guinea pigs sensitized and challenged with ovalbumin. METHODS: 34 sensitized guinea pigs were challenged with the aerosol of either saline (group A, n= 7) or 0.04% (group B, n= 7), 0.2% (group C, n= 8) and 1% (group D, n= 12) of ovalbumin. 24 hours later, cough response to inhaled capsaicin and airway responsiveness to inhaled methacholine (PC₁₅₀) were measured. Total cell number and differentials in bronchoalveolar lavage were analyzed. RESULTS: After challenge, one animal in group C and five animals in group D died from severe wheezing. With ascending concentration of ovalbumin, cough frequency induced by inhaled capsaicin increased from (6±2) times/3 min in group A to (22±4) times/3 min in group D( P< 0.05). PC₁₅₀, which did not change in group B, increased in both group C and group D significantly in addition to an increase in total cell number and eosinophils in bronchoalveolar lavage. Cough response to inhaled capsaicin was positively correlated with total cell number ( r= 0.84, P< 0.01) and eosinophils ( r= 0.78, P< 0.01) in bronchoalveolar lavage, and negatively correlated with PC₁₅₀ ( r= -0.78, P< 0.01). There was a negative correlation between PC₁₅₀ and total cell number ( r= -0.80, P< 0.01) or eosinophils ( r= -0.85, P< 0.01). CONCLUSION: Cough response in sensitized guinea pigs is enhanced and finally develops into wheezing with a progress in eosinophilic airway inflammation.     

Relationship between fibrosis and remodeling of gap junction in atrium of patients with atrial fibrillation

AIM: To examine fibrosis and remodeling of gap junction in atrial myocardium of patients with or without atrial fibrillation and to investigate the relationship between them. METHODS: Right atrial appendage (RAA) samples were collected from 44 patients with rheumatic heart disease during heart operation, 28 of which were clinically diagnosed as atrial fibrillation (AF), the left remained sinus rhythm (SR). Fibrosis and remodeling of connexin 43 were examined by polarization microscope and microscopy respectively, and analyzed with an image analyzer. Meanwhile, intercalated disc was counted under transmission electron microscope. The collagen volume fraction of type I (CVF-I) and the volume fraction of Cx43 (Cx43VF) were studied between groups of atrial fibrillation and sinus rhythm. The relationship between CVF-I and fraction of remodeled intercalated disc was studied as well. RESULTS: (1) Polarization microscope demonstrated that CVF-I collagen increased (P<0.01) in atrial fibrillation group. (2) The ratio of remodeled of intercalated disc in patients with AF was higher (P<0.01) than that in SR group whereas the number of intercalated disc was not different (P>0.05) between the two groups. (3) Cx43VF decreased (P<0.01) in the AF patients compared to those with SR. (4) A positive correlation between fibrosis and the remodeling of intercalated disc (r=0.96, P<0.01) was observed. The CVF-I was negatively correlated with the Cx43VF (r=-0.98, P<0.01). CONCLUSION: These results suggest that both fibrosis of atrial muscle and remodeling of intercalated disc are involved in the pathogenesis of human atrial fibrillation. Fibrosis of atrial muscle may play an important role in the process of atrial fibrillation by interfering with remodeling of intercalated disc and thereby involves in the remodeling of connexins.     

Correlation between myocardial interstitial collagen remodeling and changes in hemodynamics in rats with myocardial infarction

AIM: To study the relationship between cardiac extracellular matrix remodeling and cardiac function after myocardial infarction. METHODS: We observed sequential changes in collagen contents and collagen Ⅰ/Ⅲ ratios in infarct zone (IZ) and non-infarct zone (NIZ) and their relationship to the parameters of left ventricular systolic and diastolic function in the rat model of myocardial infarction induced by ligation of left main coronary artery. RESULTS: Collagen conteants in IZ and NIZ after 3d of myocardial infarction were significantly higher than those in sham group at corresponding time (P<0.05, P<0.01). Collagen Ⅰ/Ⅲ ratio in IZ decreased on day 3, significantly increased after 7 d (P<0.01). Collagen Ⅰ/Ⅲ ratio in NIZ increased significantly afte14 d. Correlated analysis between collagen contents in IZ or NIZ and collagen type Ⅰ/Ⅲ ratio and maximal ascending velocity (+p'_max) or maximal descending velocity of the left ventricular pressure (-p'_max) was performed and the negative correlation between collagen contents in NIZ and +P'_max (r=-0.589, P>0.05) and -P'_max (r=-0.788, P<0.01) was found. Collagen content in IZ positively correlated to the +P'_max (r=0.70, P<0.50), but not to -P'_max (r=-0.29, P>0.05). Collagen type Ⅰ/Ⅲ ratios in NIZ correlated negatively to the +P'_max (r=-0.504, P>0.05) and -P'_max (r=-0.545, P>0.05), but there were no relationship between collagen type Ⅰ/Ⅲ ratios in IZ and +P'_max or -P'_max in IZ. CONCLUSION: Collagen deposition in IZ after myocardial infarction was of benefit to improvement of systolic function. Collagen deposition in NIZ was harmful to systolic and diastolic function.     

Relationship between high mobility group box-1 protein and inflammation

High mobility group box-1 (HMGB1) distributed widely. It exists in many organs. HMGB1 locates in nuclei and cytoplasm in normal condition. It involves in many activity of life (i.e., duplication of DNA, cellular differentiation, gene expression). The immunocytes (i.e., mononuclear macrophage and dendritic cells) secrete HMGB1 into the extracellular milieu when stimulated with LPS and cytokines. It acts as proinflammatory cytokines, activates inflammatory and immunological responses. As a late mediators of inflammation and last long, HMGB1 plays an important role in sepsis, so it may be a convenient and practical index in evaluating severity of sepsis and may be an important and new therapeutic target in sepsis. It has been initially proved in experimental and clinical study.     

Dynamic observation of asthma model induced by allergen in mice from acute inflammation to chronic remodeling

AIM: To dynamically observe and compare the relative changes of the indexes from the process of acute inflammation to chronic remodeling in asthmatic mice induced by ovalbumin (OVA).METHODS: Female BALB/c mice (n=60) were randomly divided into normal control group and asthma group. The mice in asthma group were sensitized and challenged by OVA, while the mice in normal group received equal volume of normal saline (NS). The challenge was performed for 3 consecutive days from the 21th day to observe the response of acute inflammation, and then the mice in different groups were challenged once per week for 5 weeks. Detailed comparisons of the dynamic changes of cell infiltration, cytokine expression and airway remodeling were conducted.RESULTS: Compared with NS group, the mice in OVA group showed a predominantly eosinophilic infiltration into the airway lumen, increased production of Th2-type cytokines, secretion of epithelial mucus and deposition of subepithelial collagen. In OVA challenge groups, the levels of inflammatory cells and inflammatory factors were remarkably higher in 24 d group, whereas the most obvious changes of goblet cell hyperplasia and airway remodeling were observed in 52 d group.CONCLUSION: Acute asthma model is sufficiently induced by 3 consecutive days of OVA challenge protocol, which is accompanied with high levels of inflammatory cells and inflammatory factors. The OVA challenge protocol once per week for 5 weeks could induce a chronic asthma model with obvious airway remodeling.     

Nitric oxide production,NOS activity and expression in pulmonary arterioles of rats with chronic hypoxic hepercapnic pulmonary hypertension

AIM: To clarify the role of nitric oxide (NO) system in development of chronic hypoxic hypercapnic pulmonary hepertension. METHODS: Male Sprague-Dawley rats were randomly divided into control group and hypoxic hypercapnic group. NO content of plasma was determined, constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS) were examined using the technique of immunohistochemistry, expression of cNOS mRNA and iNOS mRNA of arteriole were detected by in situ hybridization. RESULTS: Plasma NO concentration, cNOS activity and cNOS mRNA expression in arteriole of chronic hypoxic hypecapnic group were significantly lower than that of control group (P<0.01); activity of iNOS and expression of iNOS mRNA in arteriole showed significantly higher compared with control. CONCLUSION: The disturbance of NO production and NOS expression in arteriole are involved in hypoxic hypercapnic pulmonary hepertension.     

Effect of polidatin on the activity of phospholipase A2and pulmonary structural remodeling in rats with hypoxia-induced pulmonary hypertension

AIM: To study the relationship between the activity of phospholipase A₂ (PLA₂) and pulmonary structural remodeling with the model of chronic isobaric hypoxic pulmonary hypertension. METHODS: 29 healthy Sprague-Dawley rats were randomly divided into normal control group, chronic hypoxic group and hypoxia plus Polidatin (PD) group. By diameter, the arteries were divided into two groups: arteries of group I (30 μm-100 μm) and group II (101 μm-200μm). The mean pulmonary arterial pressure (mPAP) was measured by inserting a microcatheter into the pulmonary artery. The PLA₂ activity was measured with modified microtitrimetic method. The pulmonary tissue and arterioles morphology changes were examined under light microscope. RESULTS: It was found that after 21 days hypoxia, the mean pulmonary arterial pressure (mPAP), the PLA₂ activity in blood and lung homogenate increased significantly. The media thickness of group I arteries increased (P<0.01) while that of group II arteries had no significant changes. The ratio of media area and adventitia of both groups was raised. Under light microscope, it was observed that pulmonary vascular endothelium proliferated, media became thickening and adventitia matrix increased. Pretreatment with PD could attenuate the changes mentioned above. CONCLUSION:PLA₂ plays an important inducing role through promotion of the pulmonary vascular structural remodeling in the formation of chronic hypoxic pulmonary hypertension.     

Comparison of vascular remodeling between small artery and aorta in spontaneous hypertensive rats

AIM: To examine the difference of vascular remodeling between aorta and small artery in sponta-neous hypertensive rats (SHR) and control rats.METHODS: Male SHR (20-week-old) were used as experiment group, and age matched male Wistar-Kyoto (WKY) rats were used as control group. The systolic blood pressure and body weight were measured once a week. At 43 weeks old, the rats were anaesthetized, blood samples were collected, and thoracic aorta and mesenteric small artery tissue were harvested. The morphological changes of the arterial tissue were observed with HE staining. The collagen and elastine fibers were detected by the Sirius red-Victoria blue staining. The protein expression of type I and Ⅲ collagens were analyzed by confocal laser-scanning microscopy and Western blot. The changes of the vascular ultrastructure were imaged by transmission electron microscopy. The expression of proliferating cell nuclear antigen (PCNA) and the cell apoptosis in the arterial wall were examined by immunohistochemical method and TdT-mediated dUTP nick and labeling (TUNEL) detection.RESULTS: The inner diameter (ID) and luminal cross-sectional area (LCSA) of mesenteric small artery were decreased, whereas ratio of wall thickness (WT) to ID (WT/ID) and ratio of wall cross-sectional area (WCSA) to LCSA (WCSA/LCSA) were increased. Meanwhile, adventitia fibroblast migrated to the media, with overload collagens, especially collagen Ⅲ. Proliferation index (PI) and apoptotic index (AI) of the mesenteric small artery wall cells were increased. The ID, LCSA, WT/ID and WCSA/LCSA of the aorta were increased. Moreover, the vascular smooth muscle cells (VSMCs) showed hypertrophy and hyperplasia, with overload collagens. The PI and AI of the aortic wall cells were increased.CONCLUSION: The difference of vascular remodeling between the aorta and small artery is significant. The small artery mainly appears hyperplasia of matrix, especially the adventitial collagen Ⅲ. Meanwhile, the cell apoptosis in the small artery wall is increased. The aorta mainly appears hyperplasia and hypertrophy of media VSMCs.     

The effect of L-arginine on protein kinase C of isolated pulmonary arterial rings from rats with hypoxia-induced pulmonary hypertension

AIM: To elucidate whether the mechanism that L-arginine can relieve hypoxia pulmonary hypertension involves inhibition of the activity of protein kinase C(PKC).METHODS: Twenty-one male Wistar rats were randomly divided into NS control, hypoxia and L-arginine(500 mg·kg^-1·d^-1, ip) treatment groups. After two-weeks treatment, mean pulmonary artery pressure (mPAP), mean systematic artery pressure (mSAP) and the ratio of the weight of right ventricle to that of left ventricle plus septum were measured, then two pulmonary arterial rings were isolated to be exposed to PDBu(a specific activator of PKC ) and observed: (1) The maximal response (P₁) to 500 nmol/L PDBu, the time required to achieve a half-maximal response to 500 nmol/L PDBu (t_1/2), the time during which the maximal response to 500 nmol/L PDBu maintained (T) and the isometric responses at different times (2, 4, 8, 12, 20, 40, 60, 80 min). The isometric response was represented as the percentage of the maximal response (P₀) of the same arterial ring to 5μmol/L phenylephrine hydrochloride (P₀%). (2) Dose-response curve in response to PDBu (10-11 000 nmol/L) and the dose producing a half-maximal response in the curve (EC₅₀). RESULTS: mPAP, RV/(LV+S), P₁, T and the isometric responses at 2, 4, 8, 20 min of NS control and L-arginine treatment groups were lower than those of hypoxic group respectively (P＜0.05), while t_1/2 and EC₅₀ were all greater than those of hypoxic group respectively (P＜0.05).CONCLUSION: The activity of PKC was augmented when rats were exposed to two-weeks normobaric hypoxia, which resulted in the increased reactivity of the isolated pulmonary arterial rings. L-arginine can inhibit the activation of PKC, which is likely part of the mechanism by which L-arginine can reduce mPAP and relieve the hypertrophy of right ventricle.