Effects of aging and hypoxia on morphology of cultured rat pulmonary arterial smooth muscle cells

AIM:To observe the effects of aging and hypoxia on morphology of cultured rat pulmonary arterial smooth muscle cells (PASMCs). METHODS:The cells were divided into four groups: young and normoxic group (A group), aging and normoxic group (B group), young and hypoxia group (C group), aging and hypoxia group (D group). Afterwards, the different morphological variation was observed by means of optical microscope, immune histochemistry and immune fluorescence. RESULTS:Huge differences in morphological characters in PASMCs in hypoxia and in normoxic were observed, particularly, the difference was clearly shown in F-actin concentration and array in the cytolymph. Compared with normoxic group, the concentration of SM-α-actin in hypoxic PASMCs group decreased sharply. CONCLUSION:Aging and hypoxia lead to morphological change in PASMCs. Both factors stimulate the phenotypic modulation in PASMCs, but the phenotypic modulation effect is more apparent in the condition of hypoxia.     

Effects of levcromakalim on pulmonary arterial endothelial cells and smooth muscle cells exposed to hypoxia

AIM:To explore the effects of levcromakalim(Lev) on pulmonary arterial endothelial cells (PAEC) and smooth muscle cells (PASMC) exposed to hypoxia and the mechanisms involved.METHODS:The effects of Lev on [Ca²⁺]_i, and expression of PKC_α, eNOS, iNOS and PDGF-B mRNA and protein levels were observed. The nitrite (NO₂^-) and entothelin-1(ET-1) concentrations in supernatant in cultured PAEC and PASMC were measured. The proliferation and apoptosis of PASMC was also detected.RESULTS:When PASMC were exposed to hypoxia, Lev reduced concentration of ET-1 in cultured cell supernatant, lowed the expression of PKC_α, iNOS and PDGF-B both at mRNA and protein levels, decreased [Ca²⁺]_i concentration, increased proliferation and promoted the apoptosis in PASMC. However, in the presence of Lev, the [Ca²⁺]_i concentration was not changed in the hypoxic PAEC. The NO₂^- concentration in cultured cell supernant and expression of eNOS at mRNA and protein levels in hypoxic PASMC and PAEC were also unchanged. The downregulated ET-1 activity in PASMC and PAEC and proliferation in PASMC involved in the inhibition of PKC_α signaling pathway.CONCLUSIONS:Lev reduce some disadvatage effect of hypoxia on PASMC and PAEC. The mechanism of Lev action may partly involve in the downregulation of PKC_α signaling functions.     

Effects of chronic hypoxia on intracellular calcium concentration in pulmonary arterial smooth muscle cells

AIM:To study the effect of chronic hypoxia (CH) on the intracellular calcium (［²⁺］_i) in pulmonary artery smooth muscle cells (PASMCs) and the role of L-type calcium channel and calcium store. METHODS:The rat chronic hypoxia model was set up and intervene the PASMCs with normal PSS, calcium-free PSS, nifedipine, and heparine respectively. The resting ［Ca²⁺］_i was determined with the Fura-2/AM calcium imaging technique. RESULTS:(1) The ［Ca²⁺］_i in CH group in normal PSS was higher than that in control group in normal PSS (P<0.05). The ［Ca²⁺］_i in CH group in normal PSS was higher than that in calcium-free PSS (P<0.05). (2) No obvious change of ［Ca²⁺］_i before and after application of nifedipine in PASMCs of CH groups was observed. (3) No difference of ［Ca²⁺］_i before and after application of heparine in PASMCs of CH groups was detected. CONCLUSION:Chronic hypoxia increased the ［Ca²⁺］_i in PASMCs. Chronic hypoxia induced increase in ［Ca²⁺］_i may relate to the influx of extracellular calcium, but not due to the L-type calcium channel or the IP3R modulation only.     

Inhibitory effect of Salidroside on the proliferation of rabbit pulmonary artery smooth muscle cells under hypoxia

AIM: To investigate the effect of Salidroside on the proliferation, DNA synthesis, intracellular Ca²⁺ content of rabbit PASMC (pulmonary artery smooth muscle cells) under hypoxia. METHODS: Techniques of cell culture, MTT test, [³H][³H][³H]-TdR incorporation, fluo-3 and confocal laser scanning microscopy were used. RESULTS: The A value of MTT and [³H][³H]-TdR incorporation of PASMC increased significantly by 62% (P＜0.05) and 138% (P＜0.01) after 24 h hypoxia. Salidroside (32×10^-5 mol/L) inhibited the action of hypoxia on the proliferation of PASMC, the A value of MTT and [³H][³H]-TdR incorporation declined significantly by 29% (P＜0.05) and 37% (P＜0.01) compared with hypoxia group. A calcium channel blocker, verapamil could also inhibit the accelerative effect of hypoxia on the proliferation of PASMC. The intracelluler Ca²⁺ content of PASMC raised markedly under hypoxia, but the effect of hypoxia on the intracelluler Ca²⁺ content could be inhibited by Salidroside. CONCLUSION: Salidroside inhibited the proliferation, DNA synthesis of PASMC induced by hypoxia. The inhibitory action of Salidroside on the increase in intracellular Ca²⁺ concentration under hypoxia might be one of the mechenisms.     

Effects of FHL1 on proliferation and migration of rat pulmonary arterial smooth muscle cells stimulated by cigarette smoke

AIM:To explore the role of four-and-a-half LIM domain 1 (FHL1) in the proliferation and migration of rat distal pulmonary arterial smooth muscle cells (PASMCs) stimulated by cigarette smoke extract (CSE). METHODS:Rat distal PASMCs were isolated and primarily cultured. The cells were divided into 6 groups: blank control group, negative transfection group, FHL1 siRNA transfection group, CSE group, CSE + negative transfection group and CSE + FHL1 siRNA transfection group. The mRNA and protein expression of FHL1 was detected by real-time PCR and Western blotting, respectively. Cell proliferation and migration were determined by CCK-8 and Transwell assays, respectively. RESULTS:CSE promoted the proliferation and migration of PASMCs, and increased the expression of FHL1 protein (P<0.01), but did not change the expression of FHL1 mRNA (P>0.05). FHL1 siRNA transfection attenuated the proliferation and migration of PASMCs induced by CSE (P<0.01). CONCLUSION: FHL1 protein is involved in CSE-induced proliferation and migration of rat PASMCs.     

Inhibitory effect of carbon monoxide on proliferation of rat pulmonary artery smooth muscle cells under anoxia

AIM: To investigate the effect of endogenous and exogenous carbon monoxide on the proliferation of pulmonary artery smooth muscle cells under anoxic condition. METHODS: Primary culture of rat PASMCs were passed every 3 days, the 3-5 passages were used. PASMCs were divided into 5 groups, cultured under normoxia and hypoxia and treated with HO inducer hemin, CO scavenger bovine hemoglobin (Hb) and exogenous carbon monoxide (CO), respectively. After 48 hours incubation under the conditions mentioned above, the following assay were carried out: 1) the MTT colorimetric assay and immunocytochemical staining were used to study the energy metabolism and the expression of proliferating cell nuclear antigen (PCNA) in PASMCs. 2) flow cytometry was used to analyze the cell cycle of PASMCs. RESULTS: In comparison with the control group, the value of MTT colorimetric assay was higher, the immunocytochemical staining of PCNA was stronger and the percentages of PASMCs in S and G₂M phases in the anoxia group were higher (P＜0.01). After treatment with hemin and CO, the above indexes were decreased (P＜0.01 or P＜0.05). But treatment with Hb made the above indexes increased (P＜0.01 or P＜0.05). CONCLUSION: The endogenous CO suppress the proliferation of PASMC in an autocrine way. Both the induction of endogenous CO by hemin and the treatment with exogenous CO could suppress the rat PASMCs' proliferation under anoxic condition.     

Effects of Gax gene transfection on proto-oncogene expression and proliferation of PASMCs in rats under hypoxia conditions

AIM: To explore the effects of Gax gene transfection on expressions of c-fos and c-jun mRNA and proliferation of pulmonary arterial smooth muscle cells (PASMCs) in rat under hypoxia.METHODS: PASMCs were transfected with Gax gene by Ad-Gax.Under normal oxygentention (21% O₂) or hypoxia (2.5% O₂) for 12 h condition,expressions of Gax mRNA and protein in PASMCs were detected by RT-PCR and immunocytochemistry.The expressions of c-fos and c-jun mRNA were evaluated by RT-PCR.［³H］-TdR incorporation was used to measure the PASMCs proliferation.RESULTS: The Gax overexpression in transfection group was confirmed by RT-PCR and immunocytochemistry.Under normal oxygentention or hypoxia,the c-fos and c-jun mRNA levels in transfection group were lower than those in the non-transfection group,respectively (P<0.05).［³H］-TdR incorporation in the transfection group was lower than that in non-transfection group (P<0.05,P<0.01).CONCLUSION: Gax overexpression might inhibit the PASMCs proliferation induced by hypoxia through downregulating the expressions of c-fos and c-jun.     

Inhibitory effect of antisense eukaryotic expression vectors for c-myc on rat airway smooth muscle cells

AIM: To observe the inhibitory effect of antisense eukaryotic expression vectors for c-myc on rat airway smooth muscle cells. METHODS: Antisense and sense eukaryotic expression vectors for c-myc pcDNA3-myc-antisense and pcDNA3-myc-sense were constructed. Lipofectin was used to introduce antisense and sense eukaryotic expression vectors for c-myc into rat. The inhibitory effect was assayed by MTT cell proliferation assay. Cell cycles were detected by flow cytometry technology. The expression of c-Myc was detected by immunohistochemistry. RESULTS: The results showed that antisense eukaryotic expression vector for c-myc inhibited rat airway smooth muscle cells proliferation. Rat airway smooth muscle cells were prohibited in S phase and the expression of c-Myc was decreased after antisense eukaryotic expression vectors for c-myc were transfected into cells. CONCLUSION: Antisense eukaryotic expression vectors for c-myc inhibit rat airway smooth muscle cell proliferation.     

Effects of EGLN1 siRNA on growth of rat pulmonary artery smooth muscle cells under hypoxic condition

AIM: To observe whether EGLN1 gene is involved in the growth of pulmonary arterial smooth muscle cells (PASMCs) during hypoxia when EGLN1 gene expression was interference by siRNA. METHODS: The rat primary pulmonary arterial smooth muscle cells were cultured, and the specific lipidosome of EGLN1 siRNA was constructed and transfected into the PASMCs. The transfected PASMCs were cultured under hypoxia or normoxia conditions, respectively. The viability of the PASMCs was detected by CCK-8 assay. The protein expression of EGLN1 and vascular endothelial growth factor (VEGF) was determined by Western blot. RESULTS: The viability of the PASMCs was increased and the protein expression of VEGF was up-regulated in the PASMCs under hypoxic condition in a time-dependent manner. In hypoxia or normoxia condition, the viability and VEGF protein expression of the PASMCs were suppressed by EGLN1 siRNA. CONCLUSION: EGLN1 gene may involve in the growth of rat PASMCs by regulating VEGF protein level under hypoxic condition.     

Calcium-sensing receptor mediates hypoxia-induced proliferation of rat pulmonary artery smooth muscle cells through PI3K pathways

AIM:To explore the signal transduction pathways of calcium-sensing receptor(CaSR) that mediates hypoxia-induced proliferation of rat pulmonary artery smooth muscle cells(PASMCs). METHODS:The expression of cyclin D1 and phosphorylated protein kinase B(p-Akt) was analyzed by Western blotting. Cell proliferation was tested using a BrdU incorporation assay, and cell cycle analysis was carried out using a flow cytometric assay. RESULTS:Hypoxia significantly increased the expression of cyclin D1 and p-Akt, the BrdU incorporation and the cell proliferation index. GdCl₃, an agonist of CaSR, amplified the effect of hypoxia. LY294002,a PI3K inhibitor, decreased the up-regulation of cyclin D1 expression and the BrdU incorporation, and also inhibited the increase in the cell proliferation index induced by hypoxia and GdCl₃ in PASMCs. CONCLUSION: The CaSR mediates hypoxia-induced proliferation of rat PASMCs through PI3K pathways.     

Effects of tetramethylpyrazine on calcinerin and proliferating cell nuclear antigen gene expression in the proliferation of vascular smooth muscle cells

AIM：To evaluate the effects of tetramethylpyrazine (TMP) on calcineurin (CaN) and proliferating cell nuclear antigen (PCNA) gene expression in the proliferation of vascular smooth muscle cells (VSMCs) treated by angiotensin Ⅱ (AngⅡ).METHODS：A cell proliferating model of VSMCs induced by AngⅡ was established.PCNA gene exprersion was observed by immunocytochemical staining and image analysis technique;Calcineurin (CaN) activity was detected by enzyme reaction phosphorus measurement.RESULTS：AngⅡ significantly stimulated the proliferation of VSMCs,cell proliferation activity,CaN activity and the expression levels of PCAN were higher than those in control (P<0.01).While treated with TMP,the CaN activity and PCNA expression were obviously lower than those in AngⅡ group (P<0.01).CONCLUSION：The VSMCs proliferation induced by AngII can be inhibited by tetramethylpyrazine significantly,and the inhibiting mechanism of TMP may be related to inhibiting CaN activity and restraining the expression of PCNA in a dose and time-dependent manner.     

Role of calcium-sensing receptor in hypoxia-induced proliferation of rat pulmonary artery smooth muscle cells

AIM: To explore the role of calcium-sensing receptor (CaSR) in rat pulmonary artery smooth muscle cells (PASMCs) and its effect on hypoxia-induced proliferation of PASMCs. METHODS: The expression and distribution of CaSRs were detected by Western blotting and immunofluorescence observation. The intracellular concentration of free calcium ([Ca]_i) was determined by confocal laser scanning microscopy. The cell viability was analyzed by MTT assay. The expression of PCNA and CaSRs was determined by Western blotting. RESULTS: CaSR protein was expressed in rat PASMCs. Hypoxia significantly increased the expression of CaSR and PCNA,[Ca]_i and the cell viability. GdCl₃ (an agonist of CaSR) or NPS2390 (an antagonist of CaSR) amplified or weakened the effect of hypoxia, respectively.CONCLUSION: CaSR is expressed in rat PASMCs. The activation of CaSR is involved in the proliferation of PASMCs induced by hypoxia.     

Effect of chronic cigarette smoking on BKCa and Kv1.5 expression in rat pulmonary arterial smooth muscle cells

AIM:To investigate the role of potassium channel expression alteration in chronic cigarette smoking-induced increase in pulmonary vascular responsiveness, the effect of chronic cigarette smoking on large-conductance calcium-activated potassium channel (BK_Ca) and voltage-dependent delayed rectifier potassium channel (Kv1.5) expression in rat pulmonary smooth muscle cells were investigated in vivo. METHODS:HE staining, immuno-histochemistry and in situ hybridization techniques were used. RESULTS: (1) Chronic cigarette smoking downregulates the protein and mRNA expression of BK_Ca in pulmonary arterial smooth muscles. (2) Chronic cigarette smoking downregulated the protein and mRNA expression of Kv1.5 in pulmonary arterial smooth muscles. (3) In big artery, BK_Ca decreased more makedly than Kv1.5, but in small artery, both of them decreased equally. CONCLUSION:Chronic cigarette smoking downregulates the levels of BK_Ca and Kv1.5 in rat pulmonary arterial smooth muscle cells in vivo, which maybe contribute to the mechanism of cigarette smoking-induced increase in pulmonary vascular responsiveness.     

Effects of simvastatin on PDGF-BB and serum-induced proliferation of vascular smooth muscle cells and on the expression of tumor suppressor gene PTEN

AIM:To observe the effect of simvastatin on the proliferation of vascular smooth muscle cells(VSMCs) induced by serum and growth factor PDGF-BB and the effect of simvastatin on the expression of PTEN,a important regulator of G₁/S cell cycle transition. METHODS:The DNA synthesis was determined by [³H]-TdR incorporation, cell cycle was examined with flow cytometry, the protein level of PTEN was measured by Western blot method. RESULTS: (1)Simvastatin inhibited [³H]-TdR incorporation in a dose dependent manner. (2) Flow cytometric DNA analysis revealed that simvastatin induced significantly enhancement of G₀/G₁ phase and decrease in S phase VSMCs.(3)Simvastatin increased protein level of PTEN and mevalonate, a metabolite of HMG-COA, reversed the effect of simvastatin on PTEN protein expression. CONCLUSION:Simvastatin may inhibit proliferation of VSMCs and retarded cell cycle in G₀/G₁ phase by increasing PTEN expression through inhibiting synthesis of mevalonate.     

Effects of inhibiting myosin light chain kinase on endothelin-1 induced proliferation and apoptosis of pulmonary arterial smooth muscle cells in rats

AIM: To investigate the effect of inhibiting myosin light chain kinase(MLCK) on endothelin-1(ET-1) induced proliferation and apoptosis of rat pulmonary artery smooth muscle cells(PASMCs). METHODS: Rat PASMCs were cultured and stimulated with ET-1. The cells were randomly divided into control group, ET-1 group and ET-1+MLCK inhibitor group(ET-1+M). Western blotting, MTT assay, [³H]-TdR incorporation and flow cytometry were employed to test the expression of myosin light chain(MLC) and MLCK, cell proliferation, cell cycle and apoptotic rate of PASMCs,respectively. The phosphorylation of MLC was determined by glycerol-PAGE coupled with Western blotting. RESULTS: Compared with control group, the protein expression of MLCK and MLC phosphorylation significantly enhanced after ET-1 stimulation. ET-1 markedly induced the proliferation and decreased the percentage of apoptotic rate in the PASMCs. However, pretreatment with ML-7, a MLCK inhibitor, significantly reversed the above effects induced by ET-1. CONCLUSION: MLCK inhibitor effectively inhibits the ET-1-induced proliferation and the cell cycle progression.     

miR-339 suppresses proliferation of pulmonary arterial smooth muscle cells via regulating IGF2BP1

AIM: The present study aimed to investigate the role of microRNA-339 miR-339 in the proliferation of pulmonary artery smooth muscle cells (PASMCs). METHODS: After treating with angiotensin Ⅱ of different concentrations for 48 h, miR-339 mimic and miR-339 inhibitor were transfected into PASMCs, respectively. CCK-8 assay and viable cell counting were performed to determine cell proliferation. The expression levels of miR-339 and PCNA mRNA were measured by RT-qPCR. The protein levels were detected by Western blot. The interaction between miR-339 and insulin-like growth factor 2 mRNA-binding protein 1(IGF2BP1) was confirmed by luciferase reporter assay. RESULTS: Angiotensin Ⅱ concentration-dependently increased cell proliferation and mRNA expression of PCNA, and decreased miR-339 expression in the PASMCs. Over-expression of miR-339 inhibited cell proliferation and mRNA expression of PCNA in the PASMCs, while mutation of miR-339 promoted cell proliferation and mRNA expression of PCNA in the PASMCs. In addition, miR-339 inhibited cell proliferation in angiotensin Ⅱ-treated PASMCs. Bioinformatics analysis showed that miR-339 targeted the IGF2BP1 3'-UTR, which was confirmed by luciferase reporter assay, and miR-339 negatively regulated the expression of IGF2BP1 in the PASMCs. More importantly, over-expression of IGF2BP1 attenuated the inhibitory effects of miR-339 on cell proliferation and mRNA expression of PCNA in the PASMCs. miR-399 over-expression suppressed phosphorylated p38 protein level but not p38 protein level. CONCLUSION: miR-339 suppresses anti-proliferative effects in PASMCs partly via regulating IGF2BP1 and p38 MAPK signaling pathway.     

Effect of diazoxide on change of H2O2 in rat pulmonary artery smooth muscle cells and proliferation of hypoxic rat pulmonary artery smooth muscle cells

AIM: To investigate the contribution of diazoxide,an opener of mitochondrial ATP-sensitive K+ channel (MitoK_ATP),and mitochondrial membrane potential (ΔΨm) to change of H₂O₂ in rat pulmonary artery smooth muscle cells (PASMCs) and to unbalance between cell proliferation and apoptosis of PASMCs induced by hypoxia.METHODS: The rat PASMCs were isolated from fresh normal lung tissues and cultured,which were divided into 6 groups,as follows: ① control group;② diazoxide group;③ 5-HD group;④chronic hypoxia group;⑤ chronic hypoxia+diazoxide group;⑥ chronic hypoxia +5-HD group.The relative change in mitochondrial potential was detected with rhodamine fluorescence (R-123) technique.The level of H₂O₂ in rat PASMCs was detected with chemiluminescence method.The proliferation of rat PASMCs was examined by cell cycle analysis and MTT colorimetric assay.RESULTS: After exposed to diazoxide for 24 h,the intensity of R-123 fluorescence,the level of H₂O₂ and the A value in normoxic rat PASMCs were significantly increased,and the apoptosis of rat PASMCs was significantly decreased as compared with control group (P<0.05).However,there were no significant changes in these tests after the rat PASMCs had been exposed to 5-HD for 24 h.Chronic hypoxia or chronic hypoxia+diazoxide markedly increased the intensity of R-123 fluorescence,the level of H₂O₂ and the A value in rat PASMCs,and also markedly decreased the apoptosis of rat PASMCs as compared with control group (P<0.05),and these changes were more significant in chronic hypoxia +diazoxide group than those in chronic hypoxia group (P<0.05).5-HD partly weakened the effect of hypoxia on the intensity of R-123 fluorescence,the level of H₂O₂,the A value and the apoptosis of rat PASMCs (P<0.05).Significant and positive correlations were found between the intracellular H₂O₂ and the R-123 fluorescence or the A value.Significant and negative correlation was found between the intracellular H₂O₂ and the apoptosis of rat PASMCs.CONCLUSION: The results suggest that the opening of MitoK_ATP followed by a depolarization of ΔΨm can contribute to the increase in the level of H₂O₂ in rat PASMCs and to the proliferation of rat PASMCs induced by hypoxia.This might be a mechanism of the development of hypoxic pulmonary hypertension.     

Effects of miR-130a on viability and apoptosis of rat basilar arterial smooth muscle cells

AIM: To investigate the regulatory effects of microRNA (miR)-130a on the biological characteristics of rat basilar arterial smooth muscle cells (BASMCs) and its underlying mechanisms. METHODS: The expression of miR-130a in rat BASMCs was measured by real-time PCR. After knockdown of miR-130a with inhibitor in the BASMCs, the cell viability, cell cycle distribution and apoptosis were detected by CCK-8 assay and flow cytometry. The expression of cell cycle-and apoptosis-related molecules, such as cyclin D1, cyclin-dependent kinase 2 (CDK2), p21, Bcl-2 and cleaved caspase-3/caspase-3 at protein levels was determined by Western blot. The growth arrest-specific homeobox protein (Gax) expression at mRNA and protein levels was determined by real-time PCR and Western blot. RESULTS: AngiotensionⅡ (AngⅡ) up-regulated the expression of miR-130a and down-regulated the expression of Gax (P<0.05). Transfection with miR-130a inhibitor partly reversed the increase in AngⅡ-induced cell viability and promoted the Gax expression. Furthermore, the early cell apoptotic rate was significantly increased after down-regulation of miR-130a (P<0.05), and the protein levels of cyclin D1, CDK2, Bcl-2 and p-Rb were significantly decreased, accompanied with the up-regulation of p21 and cleaved caspase-3 (P<0.05). CONCLUSION: Down-regulation of miR-130a restrains the viability and promotes the apoptosis of BASMCs by promoting Gax expression and regulating cell cycle-and apoptosis-related molecules, suggesting that miR-130a may be a potential therapeutic target of brain vascular remodeling during hypertension.