Changes of hypoxia inducible factor 1 alpha and heme oxygenase 1 in the process of hypoxic pulmonary hypertension development in rats

AIM: To observe the expression of hypoxia inducible factor-1α (HIF-1α) gene and heme oxygenase-1 (HO-1) gene in pulmonary arteries in hypoxic rats. METHODS: Forty male Wistar rats were exposed to hypoxia for 0, 3, 7, 14 or 21 days. Mean pulmonary pressure (mPAP), vessel morphometry, right ventricle hypertrophy index (RVHI) were measured. Lungs were either inflation fixed for immunohistochemistry and in situ hybridization or frozen for later measurement of HO-1 enzyme activity. RESULTS: During hypoxia, mPAP increased to significantly higher values than the control values after 7-day of hypoxia，reaching its peak after 14-day of hypoxia, then remained on the high level. Pulmonary artery remodeling developed significantly after 14-day of hypoxia. Expression of HIF-1α protein in control was poorly positive, but was up-regulated in pulmonary arterial tunica intimae of all hypoxic rats. In pulmonary arterial tunica media, the levels of HIF-1α protein were markedly up-regulated after 3-day and 7-day of hypoxia, then tended to decline after 14-day and 21-day of hypoxia. HIF-1α mRNA staining was poorly positive in control, hypoxia for 3 days and hypoxia for 7 days, but began to enhance significantly after 14-day of hypoxia, then remained stable. Expression of HO-1 protein began to increase after 7-day of hypoxia, reaching its peak after 14-day of hypoxia, then remained stable. Expression of HO-1 mRNA began to increase after 3-day of hypoxia, reaching its peak after 7-day of hypoxia, then declined. CONCLUSION: HIF-1α and HO-1 are both involved in the pathogenesis of hypoxia-induced pulmonary hypertension in rats. Furthermore, HIF-1α may inter-regulate with HO-1 gene in this process.     

Relationship between expression of heme oxygenase-1 mRNA and pulmonary hypertention induced by hypoxic hypercapnia

AIM: To study the effect of chronic hypoxic hypercapnia on expression of heme oxygenase-1 (HO-1). METHODS: Sprague-Dawley rats were randomly divided into three groups: control group(A),hypoxic hypercapnic group(B), hypoxic hypercapnia+hemin group(C). HO-1 and HO-1 mRNA were observed in pulmonary arterioles by the technique of immunohistochemistry and in situ hybridization. RESULTS: ① mPAP and weight ratio of right ventricle (RV) to left ventricle plus septum (LV+S) were significantly higher in rats of B group than those of A and C group (P<0.01). Differences of mCAP were not significant in three groups(P>0.05). ② Blood CO concentration was significantly higher in rats of B group than that of A group (P<0.01), it was much higher in C group than that of B group(P<0.01). ③ Light microscopy showed that vessel well area/total area (WA/TA), density of medial smooth muscle cell (SMC) and media thickness of pulmonary arterioles were much higher in rats of B group than those of A and C group (P<0.01). ④ The observation by electron microscopy showed proliferation of medial smooth muscle cells and collageous fibers of pulmonary arterioles in rats of B group, hemin could reverse the changes mentioned above. ⑤ HO-1 and HO-1 mRNA in pulmonary arterioles was significantly higher in rats of B group than those of A group(P<0.01), and they were significantly higher in rats of C group than those of B group (P<0.01). CONCLUSION: Expression of HO-1 mRNA and HO-1 in pulmonary arterioles was enhanced by hypoxic hypercapnia. Hemin partly inhibited pulmonary hypertension and pulmonary vessel remodeling by enhancing the expression of HO-1 mRNA and HO-1.     

The regulation of nitric-oxide synthase/nitric-oxide system by endogenous carbon monoxide in rats with pulmonary hypertension

AIM:To study the role and the mechanism of heme oxygenas/endogenous carbon monoxide on nitric oxide synthase/nitric oxide system in rats with pulmonary hypertension induced by hypoxic hypercapnia.METHODS:Sprague-Dawley rats were randomly divided into three groups: control group (A group), hypoxic hypercapnic group (B group), hypoxic hypercapnia+hemin group (C group). Blood CO concentration (COHb%), NO concentration, HO-1 activity, iNOS, cNOS in blood serum and lung homogenate were measured, respectively. RESULTS:① mPAP and RV/(LV+S) of B group were significantly higher than those of A and C group(P＜0.01).② Blood CO concentration, activity of HO-1in blood serum and lung homogenate in rats of B group were significantly higher than those of A group, but were significantly lower than those of C group (P＜0.01). ③ NO concentration in blood serum and lung homogenate in rats of B group were significantly lower than those of A group, those of C group were significantly higher than those of B group (P＜0.01).④The activity of iNOS in blood serum and lung homogenate in rats of B group were significantly higher than those of A group, but were significantly lower than those of C group (P＜0.01). Activity of cNOS in blood serum and lung homogenate of B group were significantly lower than those of A group (P＜0.01), and there was no significant difference between cNOS in B and C group.CONCLUSION:Endogenous carbon monoxide upregulated iNOS/NO system in rats with chronic pulmonary hypertension induced by hypoxic hypercapnia.     

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.     

Effect of ligustrazine on hydrogen sulfide system in lung tissue of rats with pulmonary hypertension induced by hypoxic hypercapnia

AIM: To investigate the effect of ligustrazine on hydrogen sulfide (H2S) system in pulmonary hypertension induced by hypoxic hypercapnia in rats. METHODS: Thirty Sprague-Dawley rats were randomly divided into 3 groups: control group (C), hypoxic hypercapnia group (HH), and hypoxic hypercapnia+ligustrazine group (HH+L). The change of hemodynamics was measured. The ratio of vessel wall area and total area of arteriae pulmonalis were observed under light microscope. The apoptosis of arteriae pulmonalis was tested with TdT-mediated dUTP nick end labeling (TUNEL), and the apoptosis index was calculated. Plasma level of hydrogen sulfide and activity of hydrogen sulfide generating enzymes in homogenates of rat lung tissue were evaluated by sensitive modified sulfide electrode method. Cystathionine-γ-lyase (CSE) mRNA in lung tissues was determined by RT-PCR. RESULTS: The level of mean pulmonary arterial pressure, the ratio of vessel wall area/total area and the right ventricle/left ventricle+septum were significantly higher in HH group than those in C group, and the value was obviously lower in HH+LTZ group than that in HH group (all P<0.01). The mean carotid arterial pressure of 3 groups had no significant difference (P>0.05). The apoptotic index of arteriae pulmonalis in HH group and HH+LTZ group was significantly lower than that in C group, and that in HH+LTZ group was significantly higher than that in HH group (P<0.05 or P<0.01). Plasma level of H2S, the activity of H2S generating enzymes in homogenates of rat lung tissue, cystathionine-γ-lyase (CSE) mRNA in lung tissues in HH group were significantly lower than those in C group (all P<0.01), and those in HH+LTZ group were significantly lower than those in HH group (all P<0.01). CONCLUSION: Ligustrazine up-regulates the expression of cystanthionine-γ-splitting enzyme (CSE), enhances the activity of CSE and increases the level of H2S to prevent pulmonary hypertension induced by hypoxic hypercapnia.     

Roles of ERK pathway and Panax notoginoside treatment in hypoxic hypercapnia pulmonary hypertension in rats

AIM: To investigate the roles of Panax notoginoside (PNS) and ERK1/2 signaling pathway in the pathological process of chronic hypoxic hypercapnia pulmonary hypertension in rats.METHODS: The animal model of chronic hypoxic hypercapnia pulmonary hypertension was set up in 72 male Sprague-Dawley rats and the animals were randomly divided into 6 groups: normal (N) group, hypoxic hypercapnia for 3-day (H_3d) group, hypoxic hypercapnia for 1-week (H_1w) group, hypoxic hypercapnia for 2-week (H_2w) group, hypoxic hypercapnia for 4-week (H_4w) group and PNS treatment (H_p) group.The rats in H_p group were injected with PNS (50 mg·kg^-1·d^-1, ip) before placing the animals into the hypoxic hypercapnia chamber.The rats in other groups were injected with normal saline (2 mL/kg, ip).The morphological changes of the pulmonary artery were observed under microscope with HE staining.Western blotting was used to detect the protein expression of p-ERK.The protein levels of p-ERK in the lung tissues and pulmonary blood vessels were determined by immunohistochemistry.RESULTS: The ratios of WA/TA in H_1w, H_2w, H_4w and H_p groups were higher than that in N group (P<0.05).The ratio of WA/TA in H_p group was obviously lower than that in H_4w group (P<0.05).The protein expression of p-ERK was barely positive in N group, but was up-regulated in the pulmonary tissues in all hypoxic rats.Compared with N group, the protein level of p-ERK was markedly up-regulated in H_3d group, reached its peak in H_2w group, and tended to decline in H_4w group (P<0.05).In pulmonary arterial tunica intima and tunica media, p-ERK protein was dramatically expressed in all hypoxic rats compared with the control animals (P<0.05).In the lung tissues, the protein level of p-ERK in H_p group was lower than that in H_4w group (P<0.05).In pulmonary arterial tunica intima and tunica media, the protein level of p-ERK in H_p group was lower by 84.86% than that in H_4w group (P<0.05).CONCLUSION: ERK1/2 as a signal transducer may play an important role in the development of hypoxia and hypercapnia induced pulmonary hypertension.PNS inhibits the expression of ERK1/2, thus attenuating the development of pulmonary hypertension and improving pulmonary vascular remodeling.     

Effect of safflower injection on expression of COX-2 mRNA and protein in chronic hypoxic hypercapnic rat pulmonary arterioles

AIM:To study the effect of safflower injection on expression of COX-2 mRNA in chronic hypoxic hypercapnic rat pulmonary arterioles.METHODS: Sprague-Dawley rats were randomly divided into normal control group, hypoxic hypercapnic group (B), hypoxic hypercapnia+ safflower injection group (C). The concentration of TXB2 and 6-Keto-PGF1α in plasma and in lung were detected by the technique of radioimmunoassay. COX-2 mRNA was observed in arterioles from rats by the technique of in situ hybridization. RESULTS: ① Mean pulmonary arterial pressure(mPAP), weight ratio of right ventricle (RV) to left ventricle plus septum (LV+S) were much higher in B group than those in control group. No significant difference of mean carotid arterial pressure(mCAP) was observed in three groups. ② The concentration of TXB2 and the ratio of TXB2/6-keto-PGF1α were significantly higher in B group than those in control group. ③ Light microscopy showed that vessel wall area/total area, the density of medial smooth muscle cells and the thickness of medial smooth cell layer were significantly higher in B group than those in control group. Electron microscopy showed proliferation of medial smooth muscle cells and collagenous fibers in pulmonary arterioles in B group. Safflower injection reversed the changes mentioned above. ④ Expression of COX-2 mRNA in pulmonary arterioles was much higher in C group than those in B group. Differences of COX-1 mRNA in pulmonary arterioles were not significant between these two groups.CONCLUSION:Safflower injection increases the expression of COX-2 mRNA in chronic hypoxic hypercapnic rat pulmonary arterioles, indicating an important mechanism that safflower injection inhibits the formation of hypoxic hypercapnia pulmonary hypertension and pulmonary vessel remodeling.     

Alteration of pulmonary vascular structure and gaseous molecules in rats with pulmonary hypertension induced by high pulmonary blood flow

AIM: To examine the alteration of pathologic structure and gaseous molecules in rats with pulmonary hypertension induced by high pulmonary blood flow.METHODS: Aortocaval shunting was produced for 11 weeks in rats, and pulmonary hemodynamics was evaluated.Pulmonary vascular micro- and ultra- structure was also examined.Meanwhile,the concentration of plasma nitric oxide (NO) and carbon monoxide (CO) was measured by spectrophotometry.The expression of endothelial nitric oxide synthase (eNOS) and heme oxygenase-1 (HO-1) in pulmonary arteries was detected by immunohistochemistry.RESULTS: After 11- week aortocaval shunting,pulmonary artery mean pressure was significantly increased.Muscularization of small pulmonary vessels and relative medial thickness and area of pulmonary arteries were obviously increased in shunting rats compared with controls.Ultrastructure of intrapulmonary arteries changed obviously in shunting rats.Meanwhile,plasma NO concentration was increased and eNOS expression in pulmonary artery endothelial cells was significantly augmented in rats of shunting group.Plasma carbon monoxide level and HO-1 expression in puomonary artery smooth muscle cells,however,were not altered in shunting rats.CONCLUSIONS: Pulmonary vascular structural remodeling is the important pathologic basis of pulmonary hypertension induced by a left-to-right shunt,and NO other than CO might play an important regulating role in the development of high pulmonary blood flow-induced pulmonary hypertension.     

The relationship between the activity of phospholipase A2 and chronic hypoxic pulmonary hypertension

AIM:To study the relationship between the activity of phospholipase A₂ (PLA₂) and chronic hypoxic pulmonary hypertension. METHODS:29 healthy SD rats were randomly divided into normal control group, chronic hypoxic group and hypoxia plus Polidatin (PD) group. The model of rat chronic hypoxic pulmonary hypertension was made by method of intermittent isobaric hypoxia for 21 days. The mean pulmonary arterial pressure (mPAP) was measured by inserting a microcatheter into the pulmonary artery. RESULTS:After exposing hypoxia for 21 days, the mPAP, R/L+S, the PLA₂ activity, TXB₂, MDA in plasma and lung homogenate increased significantly, while 6-k-PGF_1α, SOD decreased significantly. Pretreatment with PD could relieve the changes mentioned above.CONCLUSION:PLA₂ plays an important inducing role through its metabolic products and the interactional radicals in the formation of chronic hypoxic pulmonary hypertension.     

Expression and distribution of osteopontin in the development of pulmonary hypertension induced by hypoxia-hypercapnia

AIM: To study the expression and distribution of osteopontin (OPN) in lungs and pulmonary arteries in pulmonary hypertensive rats induced by hypoxia-hypercapnia, and to explore the role of OPN in pathogenesis of pulmonary hypertension. METHODS: Forty-eight male Sprague-Dawley rats (Weight 180 g-220 g) were randomly divided into four groups: normal control group (NC), hypoxic hypercapnia 1-week，2-week and 4-week group (1HH, 2HH and 4HH). The expressions of OPN mRNA and protein in lungs and pulmonary arteries were detected by RT-PCR and immunohistochemistry. ELISA was used to detect the concentration of OPN in lung homogenates. The content of OPN in pulmonary arteries was detected by Western blotting. RESULTS: ① The mean pulmonary artery pressure (mPAP) and weight ratio of right ventricle to left ventricle and septum ［RV/(LV+S)］ in all hypoxic hypercapniac groups were higher than those in normal control group (P<0.01), respectively. Differences of mean carotid artery pressure (mCAP) among these four groups were not significant (P>0.05). ② The expression of OPN mRNA was significantly increased in pulmonary arteries and lung tissues in hypoxic hypercapnic groups compared with normal control group (P<0.01). ③ The result of immunohistochemistry showed that OPN was only detected in bronchus and alveolar epithelium, but not detected in pulmonary arterioles of normal control group. In contrast，OPN expression was evident in pulmonary arterioles of 1HH rats，especially in media. Moreover, the expression of OPN was markedly increased in group 2HH and 4HH. ④ OPN levels in lung homogenates in 1HH, 2HH and 4HH were increased by 69%, 128% and 187% (P<0.01), respectively, compared with control rats. ⑤ Western blotting analysis showed that the contents of OPN were significantly higher in all hypoxic hypercapnic groups than those in NC group (P<0.01).CONCLUSION: The expressions of OPN in pulmonary arteioles and lung are increased in rats with pulmonary hypertension. OPN might play an important role in the pathogenesis of pulmonary hypertension induced by chronic hypoxia and hypercapnia.     

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.     

Phosphatidylinositol 3-kinase regulates hypoxia-inducible factor 1α in pulmonary arteries of rats with hypoxia-induced pulmonary hypertension

AIM:To investigate relationship among phosphatidylinositol 3-kinase (PI3K) and hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) in lung of rats with hypoxia-inducible pulmonary hypertension. METHODS:Forty male adult Wistar rats were randomly divided into five groups (eight rats in each group):control group (C group) and groups with hypoxia for 3, 7, 14 and 21 days (H3, H7, H14 and H21 group). Mean pulmonary arterial pressure (mPAP), right ventric hypertrophy index (RVHI) and vessel morphometry were measured. The levels of HIF-1α mRNA expression in lung tissue was measured by in siteu hybridization (ISH). The protein expression of HIF-1α，VEGF and phosphorylated protein kinase β (P-AKT) were observed by immunohistochemistry or Western blotting. RESULTS:mPAP increased significantly 7 days after hypoxia ［(23.53±1.78) mmHg］, peaked 14 days after hypoxia, then remained on the high level. Pulmonary artery remodeling index (extern diameter 100 μm) and RVIH became evident 14 days after hypoxia. Expression of P-AKT protein in control group was poorly positive, but was up-regulated in pulmonary arterial tunica intima and tunica media in all hypoxia rats. HIF-1α mRNA staining was poorly positive in control，hypoxia for 3 days and hypoxia for 7 days, but began to increase significantly 14 days after hypoxia (0.305±0.104, P<0.05), then remained stable. Expression of HIF-1α protein in control group was poorly positive, but was up-regulated in pulmonary arterial tunica intima in all hypoxic rats. In pulmonary arterial tunica media, the levels of HIF-1α protein was markedly up-regulated after 3 days (0.029±0.019, P<0.05 ), reached its peak 7 days after hypoxia (0.232±0.008, P<0.05), then tended to decline 14 days and 21 days after hypoxia. Expression of VEGF protein began to increase 7 days after hypoxia (0.188±0.018, P<0.05), reached its peak 14 days after hypoxia (0.238±0.017, P<0.05), then remained on the high level in pulmonary arterial tunica intima. Linear correlation analysis showed that P-AKT, HIF-1α mRNA, VEGF and mPAP were correlated with vessel the morphometry and RVHI (P<0.01). P-AKT was positively correlated with HIF-1α and VEGF (tunica intima). CONCLUSION:P-AKT, HIF-1α and VEGF are all involved in the pathogenesis of hypoxia-induced pulmonary hypertension in rats.     

Effects of adipose tissue-derived mesenchymal stem cells on calcium channels of pulmonary artery in rats with pulmonary arterial hypertension induced by monocrotaline

AIM: To investigate the effects of adipose tissue-derived mesenchymal stem cells (ADMSCs) on calcium channels of pulmonary artery in monocrotaline (MCT)-induced pulmonary hypertensive rats.METHODS: ADMSCs were isolated from adipose tissue by collagenase digestion. Twenty-four Sprague-Dawley rats were randomly divided into 3 groups: normal control (Ctr) group, pulmonary arterial hypertension (PAH) group and ADMSCs transplantation group. Mean pulmonary arterial pressure (MPAP) was measured by catheterization, and right ventricular hypertrophy index (RVHI) was calculated. The expression of voltage-gated calcium channel α1c subunit (CaVα1c), sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA-2a), inositol 1,4,5-triphosphate receptor 1(IP3R-1), transient receptor potential channel 1 (TRPC1) and TRPC6 at mRNA and protein levels in the pulmonary trunks was determined by RT-PCR and Western blotting, respectively.RESULTS: MPAP and RVHI were higher in PAH group than those in Ctr group, while those in ADMSCs group were significantly decreased as compared with PAH group. The expression of CaVα1c, TRPC1 and TRPC6 at mRNA and protein levels was obviously increased in PAH group as compared with Ctr group, while that in ADMSCs group was significantly decreased as compared with PAH group. Compared with Ctr group, the expression of SERCA-2a and IP3R-1 at mRNA and protein levels was obviously decreased in PAH group, while that in ADMSCs group was significantly increased as compared with PAH group.CONCLUSION: MPAP and RVHI are attenuated by ADMSCs in MCT-induced pulmonary hypertensive rats. The reduction of pulmonary arterial pressure by ADMSCs transplantation in MCT-induced pulmonary hypertensive rats may be related to the changes of calcium channels.     

Levels of CGRP and ET-1 in plasma of pulmonary artery and thoracic aorta and in the extractives of lung and ventricular tissues of the chronic hypoxic rats

AIM AND METHODS: To explore the effects calcitonin gene-related peptide (CGRP) and endothelin-1(ET-1) on the mechanisms of hypoxic pulmonary hypertension (HPH), the contents of CGRP and ET-1 in plasma of pulmonary artery and thoracic aorta and in extractives of lung and ventricular tissues of the chronic hypoxic rats were determined by radioimmunoassay. The changes of their hemodynamic indices and right heart hypertrophy index were monitored simultaneously. RESULTS: The level of pulmonary artery plasma CGRP was significantly higher than that of thoracic aorta plasma, but just the reverse was ET-1 or the ratio of ET-1 and CGRP in control rats( P<0.01). Compared with controls, the level of pulmonary artery plasma CGRP was gradually reduced in all hypoxic rats, but ET-1 was enhanced after 7 and 14 days of hypoxia and was decreased after 21 days of hypoxia. With prolonging time exposed to hypoxia, the level of thoracic aorta plasma CGRP was markedly increased in hypoxic animals compared with controls ( P<0.05), the positive correlation significantly with increased pulmonary arterial pressure( r = -0.896, P =0.05), but the lower level of thoracic aorta plasma ET-1 showed or negative correlation with pulmonary arterial pressure. CONCLUSIONS: These data suggest that the unbalance of effects of CGRP and ET may plays an important role in regulating the resistance of pulmonary circulation and has close relation with the formation of HPH.     

The expression of adrenomedullin mRNA in the right ventricle in chronic hypoxic rats

AIM: To study the role of adrenomedullin(AM) in the pathogenesis of hypoxic pulmonary hypertension. METHODS: Rats were exposed to chronic hypoxia for 14 days. After the measurement of the right ventricular systolic pressure (RVSP), the rats were executed. The weight of the right ventricle (RV), the left ventricle(LV) and the ventricular septum(SP) were determined. The ration RV/(LV+SP) was used to express the thickness of RV. In situ hybridization was used for the detection of the expression of AM mRNA in the lung and RV. RESULTS: The RVSP in the hypoxic group was (63.63±3.42) mmHg,which was significantly higher than that in control group [(34.13±3.40) mmHg]. The RV/(LV+SP) in hypoxic group was 0.439±0.039,which was increased obviously when compared with that of control (0.230±0.025). The level of AM mRNA expressed in the RV in the hypoxia group was significantly higher than that in the control group. CONCLUSION: The expression of AM mRNA in RV increased in the hypoxic condition, which suggests that AM may attenuate the inappropriate increase in pulmonary artery pressure.     

Effect of heme oxygenase on vascular remodeling in renal hypertension

AIM: To investigate the effect of heme oxygenase on vascular remodeling in renal hypertension. METHODS: Male Wistar rats were randomly divided into sham-operated, 2K1C （two-kidney one-clip） and hemin-induced groups. Four weeks after the treatments, the thickness of aortic media and HO enzymatic activity of the aorta were determined. Immunohistochemical staining was carried out to detect protein of HO-1 in the aorta. RESULTS: The blood pressure in 2K1C renal hypertension rats started to increase two weeks after the surgery and stabled at a high level at the 4th week. Hemin, an inducer of HO-1, markedly inhibited the increase in blood pressure. Aortic medium thickness of the 2K1C rats at 4th week was 27.5% thicker than that in the sham-operated rats. The thickness of aortic medium of the hemin-induced rats was 16.1% less than that in 2K1C group. At the 4th week after operation, protein level and enzymatic activity of HO-1 in aorta were higher than that in 2K1C group compared to those in the sham-operated group. CONCLUSION: Renal hypertension caused vascular remodeling and the activation of HO-1. HO-1 induction decreased the blood pressure of renal hypertension and reduced vascular remodeling.     

Changes of heme oxygenase-carbon monoxide system-in vascular calcification in rats

AIM:To investigate the change of heme oxygenase (HO)-carbon monoxide (CO)-cyclic guanosine monophosphate (cGMP) pathway in vascular calcification, to clarify the cellular and molecular mechanimsm in vascular calcification.METHODS:Vascular calcification model was established in rats by using vitamin D₃ and nicotine. The relative content of HO-1 mRNA, immunochemistry (IH) for HO-1, HO activity, HbCO formation and content of cGMP in aorta were measured.RESULTS:Compared to those of control rats, the HO-1 mRNA level in vessels of rats in VDN group(vascular calcification group) were decreased by 34.9% (P＜0.05);expression of HO-1 protein were decreased too, there were trace positive staining of HO-1 in the endothelium, and no obvious immunoreactivity in the medial layer;HO-1 activity was decreased by 60.6% (P＜0.01), CO concentration was decreased by 53.9% (P＜0.01) and cGMP content was decreased by 77.1% (P＜0.01) in vessels of rats in VDN group.CONCLUSION:There were obvious down regulation in HO-CO-cGMP pathway in calcified vessels.     

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.