scholarly journals Micro-RNA-1 is decreased by hypoxia and contributes to the development of pulmonary vascular remodeling via regulation of sphingosine kinase 1

2018 ◽  
Vol 314 (3) ◽  
pp. L461-L472 ◽  
Author(s):  
Justin R. Sysol ◽  
Jiwang Chen ◽  
Sunit Singla ◽  
Shuangping Zhao ◽  
Suzy Comhair ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Vascular Remodeling ◽  
Molecular Mechanisms ◽  
Sphingosine Kinase ◽  
Sphingosine Kinase 1 ◽  
Pulmonary Vascular Remodeling ◽  
Micro Rnas ◽  
And Migration ◽  
Proliferation And Migration

Sphingosine kinase 1 (SphK1) upregulation is associated with pathologic pulmonary vascular remodeling in pulmonary arterial hypertension (PAH), but the mechanisms controlling its expression are undefined. In this study, we sought to characterize the regulation of SphK1 expression by micro-RNAs (miRs). In silico analysis of the SphK1 3′-untranslated region identified several putative miR binding sites, with miR-1-3p (miR-1) being the most highly predicted target. Therefore we further investigated the role of miR-1 in modulating SphK1 expression and characterized its effects on the phenotype of pulmonary artery smooth muscle cells (PASMCs) and the development of experimental pulmonary hypertension in vivo. Our results demonstrate that miR-1 is downregulated by hypoxia in PASMCs and can directly inhibit SphK1 expression. Overexpression of miR-1 in human PASMCs inhibits basal and hypoxia-induced proliferation and migration. Human PASMCs isolated from PAH patients exhibit reduced miR-1 expression. We also demonstrate that miR-1 is downregulated in mouse lung tissues during experimental hypoxia-mediated pulmonary hypertension (HPH), consistent with upregulation of SphK1. Furthermore, administration of miR-1 mimics in vivo prevented the development of HPH in mice and attenuated induction of SphK1 in PASMCs. These data reveal the importance of miR-1 in regulating SphK1 expression during hypoxia in PASMCs. A pivotal role is played by miR-1 in pulmonary vascular remodeling, including PASMC proliferation and migration, and its overexpression protects from the development of HPH in vivo. These studies improve our understanding of the molecular mechanisms underlying the pathogenesis of pulmonary hypertension.

scholarly journals Deficiency of Akt1, but not Akt2, attenuates the development of pulmonary hypertension

2015 ◽  
Vol 308 (2) ◽  
pp. L208-L220 ◽  
Author(s):  
Haiyang Tang ◽  
Jiwang Chen ◽  
Dustin R. Fraidenburg ◽  
Shanshan Song ◽  
Justin R. Sysol ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Pulmonary Hypertension ◽  
Smooth Muscle ◽  
Vascular Remodeling ◽  
Pulmonary Vascular Remodeling ◽  
Akt Isoforms ◽  
Cell Proliferation And Migration ◽  
Pulmonary Arterial ◽  
And Migration ◽  
Proliferation And Migration

Pulmonary vascular remodeling, mainly attributable to enhanced pulmonary arterial smooth muscle cell proliferation and migration, is a major cause for elevated pulmonary vascular resistance and pulmonary arterial pressure in patients with pulmonary hypertension. The signaling cascade through Akt, comprised of three isoforms (Akt1–3) with distinct but overlapping functions, is involved in regulating cell proliferation and migration. This study aims to investigate whether the Akt/mammalian target of rapamycin (mTOR) pathway, and particularly which Akt isoform, contributes to the development and progression of pulmonary vascular remodeling in hypoxia-induced pulmonary hypertension (HPH). Compared with the wild-type littermates, Akt1 −/− mice were protected against the development and progression of chronic HPH, whereas Akt2 −/− mice did not demonstrate any significant protection against the development of HPH. Furthermore, pulmonary vascular remodeling was significantly attenuated in the Akt1 −/− mice, with no significant effect noted in the Akt2 −/− mice after chronic exposure to normobaric hypoxia (10% O2). Overexpression of the upstream repressor of Akt signaling, phosphatase and tensin homolog deleted on chromosome 10 (PTEN), and conditional and inducible knockout of mTOR in smooth muscle cells were also shown to attenuate the rise in right ventricular systolic pressure and the development of right ventricular hypertrophy. In conclusion, Akt isoforms appear to have a unique function within the pulmonary vasculature, with the Akt1 isoform having a dominant role in pulmonary vascular remodeling associated with HPH. The PTEN/Akt1/mTOR signaling pathway will continue to be a critical area of study in the pathogenesis of pulmonary hypertension, and specific Akt isoforms may help specify therapeutic targets for the treatment of pulmonary hypertension.

scholarly journals Overexpressed lncRNA AC068039.4 contributes to proliferation and cell cycle progression of pulmonary artery smooth muscle cells via sponging miR-26a-5p/TRPC6 in hypoxic pulmonary arterial hypertension

2020 ◽  
Author(s):  
Yuhan Qin ◽  
Boqian Zhu ◽  
Linqing Li ◽  
Gaoliang Yan ◽  
Dong Wang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Pulmonary Hypertension ◽  
Smooth Muscle ◽  
Vascular Remodeling ◽  
Cell Cycle Progression ◽  
Cycle Progression ◽  
Pulmonary Vascular Remodeling ◽  
Pulmonary Artery Smooth Muscle ◽  
And Migration ◽  
Proliferation And Migration

Abstract Background: Hypoxic pulmonary hypertension (HPH) is a devastating and incurable disease characterized by pulmonary vascular remodeling, resulting to right heart failure and even death. Accumulated evidence has confirmed long coding RNAs (lncRNAs) are involved in hypoxia induced pulmonary vascular remodeling in HPH. The exact mechanism of lncRNA in hypoxic pulmonary hypertension remains unclear. Methods：Microarray analysis was applied to investigate the profiles of lncRNA expression in pulmonary artery smooth muscle cells (PASMCs) cultured under hypoxia and normoxia condition. qRT-PCR was performed for the expression of lncRNAs, miRNA and mRNAs, western blot analysis was employed for detection the expression of proteins. CCK-8 and transwell chamber assay were applied for assessment of PASMC proliferation and migration, respectively. Besides, flow cytometry was performed for assessments of cell cycle progression. The binding between AC068039.4 and miR-26a-5p, miR-26a-5p and TRPC6 3’UTR were detected by dual luciferase reporter assay.Results：A total of 1211 lncRNAs (698 up-regulated and 513 down-regulated) were differently expressed in hypoxia induced PASMCs. Consistent with microarray analysis, quantitative PCR verified that AC068039.4 was obviously up-regulated in hypoxia induced PASMCs. Knocking down AC068039.4 alleviated proliferation and migration of PASMCs and regulated cell cycle progression through inhibiting cells entering the G0/G1 cell cycle phase. Further experiment indicated AC068039.4 promoted hypoxic PASMCs proliferation via sponging miR-26-5p. In addition, transient receptor potential canonical 6 (TRPC6) was confirmed to be a target gene of miR-26a-5p. Conclusion: In conclusion, downregulation of lncRNA AC068039.4 inhibited pulmonary vascular remodeling through AC068039.4/miR-26a-5p/TRPC6 axis, providing new therapeutic insights for the treatment of HPH.

scholarly journals Cyr61 promotes Schwann cell proliferation and migration via αvβ3 integrin

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Zhenghui Cheng ◽  
Yawen Zhang ◽  
Yinchao Tian ◽  
Yuhan Chen ◽  
Fei Ding ◽  
...  
Keyword(s):  
Nerve Injury ◽  
Peripheral Nerves ◽  
Molecular Mechanisms ◽  
Αvβ3 Integrin ◽  
Promoting Effect ◽  
Ccn Family ◽  
And Migration ◽  
Proliferation And Migration

Abstract Background Schwann cells (SCs) play a crucial role in the repair of peripheral nerves. This is due to their ability to proliferate, migrate, and provide trophic support to axon regrowth. During peripheral nerve injury, SCs de-differentiate and reprogram to gain the ability to repair nerves. Cysteine-rich 61 (Cyr61/CCN1) is a member of the CCN family of matrix cell proteins and have been reported to be abundant in the secretome of repair mediating SCs. In this study we investigate the function of Cyr61 in SCs. Results We observed Cyr61 was expressed both in vivo and in vitro. The promoting effect of Cyr61 on SC proliferation and migration was through autocrine and paracrine mechanisms. SCs expressed αvβ3 integrin and the effect of Cyr61 on SC proliferation and migration could be blocked via αvβ3 integrin. Cyr61 could influence c-Jun protein expression in cultured SCs. Conclusions In this study, we found that Cyr61 promotes SC proliferation and migration via αvβ3 integrin and regulates c-Jun expression. Our study contributes to the understanding of cellular and molecular mechanisms underlying SC’s function during nerve injury, and thus, may facilitate the regeneration of peripheral nerves after injury.

scholarly journals MiRNA let-7b promotes the development of hypoxic pulmonary hypertension by targeting ACE2

2019 ◽  
Vol 316 (3) ◽  
pp. L547-L557 ◽  
Author(s):  
Ruifeng Zhang ◽  
Hua Su ◽  
Xiuqing Ma ◽  
Xiaoling Xu ◽  
Li Liang ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Hypoxia Inducible Factor ◽  
Underlying Mechanism ◽  
Pulmonary Vessel ◽  
Hypoxic Pulmonary Hypertension ◽  
And Migration ◽  
Ventricle Hypertrophy ◽  
Proliferation And Migration

Angiotensin-converting enzyme 2 (ACE2) protects against hypoxic pulmonary hypertension (HPH) by inhibiting the proliferation and migration of pulmonary artery smooth muscle cells (PASMCs). Under hypoxia, the hypoxia-inducible factor 1α (HIF-1α) inhibits ACE2 indirectly; however, the underlying mechanism is unclear. In the present study, we found that exposure to chronic hypoxia stimulated microRNA (miRNA) let-7b expression in rat lung via a HIF-1α-dependent pathway. Let-7b downregulated ACE2 expression by directly targeting the coding sequence of ACE2. Our in vitro and in vivo results revealed that let-7b contributed to the pathogenesis of HPH by inducing PASMCs proliferation and migration. Let-7b knockout mitigated right ventricle hypertrophy and pulmonary vessel remodeling in HPH by restoring ACE2 expression. Overall, we demonstrated that HIF-1α inhibited ACE2 expression via the HIF-1α-let-7b-ACE2 axis, which contributed to the pathogenesis of HPH by stimulating PASMCs proliferation and migration. Since let-7b knockout alleviated the development of HPH, let-7b may serve as a potential clinical target for the treatment of HPH.

scholarly journals Identification of a Novel Gene Correlated With Vascular Smooth Muscle Cells Proliferation and Migration in Chronic Thromboembolic Pulmonary Hypertension

2021 ◽  
Vol 12 ◽  
Author(s):  
Feng Wang ◽  
Congrui Sun ◽  
Xiaoshuo Lv ◽  
Mingsheng Sun ◽  
Chaozeng Si ◽  
...  
Keyword(s):  
Vascular Remodeling ◽  
Molecular Mechanisms ◽  
Kegg Pathway ◽  
Chronic Thromboembolic Pulmonary Hypertension ◽  
Vsmc Proliferation ◽  
Kegg Pathway Analysis ◽  
Tnf Α ◽  
Thromboembolic Pulmonary Hypertension ◽  
And Migration ◽  
Proliferation And Migration

Objective: Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by thrombofibrotic obstruction of the proximal pulmonary arteries, which result in vascular remodeling of the distal pulmonary artery. While the cellular and molecular mechanisms underlying CTEPH pathogenesis remain incompletely understood, recent evidence implicates vascular remodeling. Here, we identify the molecular mechanisms that contribute to vascular remodeling in CTEPH.Methods: Microarray data (GSE130391) for patients with CTEPH and healthy controls were downloaded from the Gene Expression Omnibus (GEO) and screened for differentially expressed genes (DEGs). DEGs were functionally annotated using Gene Ontology (GO) functional analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. A protein–protein interaction (PPI) network was constructed to identify hub genes. Finally, pulmonary artery samples were harvested from patients with CTEPH (n = 10) and from controls (n = 10) and primary vascular smooth muscle cells (VSMCs) were cultured. Effects of the proto-oncogene FOS on VSMC proliferation and migration were assessed using expression and knockdown studies.Results: We detected a total of 292 DEGs, including 151 upregulated and 141 downregulated genes. GO analysis revealed enrichment of DEGs in biological processes of signal transduction, response to lipopolysaccharide, signal transduction, and myeloid dendritic cell differentiation. Molecular function analysis revealed enrichment in tumor necrosis factor (TNF)-activated receptor activity, transcriptional activator activity, and protein homodimerization activity. The expression of TNF-α and its receptor (sTNFR1 and sTNFR2) were significantly higher in CTEPH group, compared with control group. KEGG pathway analysis revealed enrichment in salmonella infection, pathways in cancer, osteoclast differentiation, and cytokine-cytokine receptor interaction. Hub genes in the PPI included FOS, suggesting an important role for this gene in vascular remodeling in CTEPH. Primary VSMCs derived from patients with CTEPH showed increased FOS expression and high proliferation and migration, which was attenuated by FOS inhibition. In control VSMCs, TNF-α treatment increased proliferation and migration, which FOS inhibition likewise attenuated.Conclusion: TNF-α drives CTEPH pathogenesis by promoting VSMC proliferation and migration via increased FOS expression. These results advance our understanding of the molecular mechanisms of vascular remodeling in CTEPH, and may inform the development of new therapeutic targets.

NPS2143 Modulates the Phenotypic Switching of PASMCs by Inhibiting Autophagy in Hypoxia-Induced Pulmonary Hypertension

2021 ◽  
Vol 8 (2) ◽  
Author(s):  
Wang L ◽  
◽  
Shao H ◽  
Che B ◽  
Wang N ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Pulmonary Hypertension ◽  
Pulmonary Artery ◽  
Western Blot ◽  
Vascular Remodeling ◽  
Pulmonary Artery Hypertension ◽  
Phenotypic Switching ◽  
Pulmonary Vascular Remodeling

Background and Objectives: Pulmonary Artery Hypertension (PAH) is considered as a malignant tumor in cardiovascular disease. Our previous study found that Calcium-Sensing Receptor (CaSR) is involved in pulmonary vascular remodeling in hypoxic pulmonary hypertension (HPH). However, the relationship of Pulmonary Artery Smooth Muscle Cell (PASMC) phenotypic switching, proliferation, and autophagy in CaSR-related HPH remain unclear. The purpose of this study was to detect the role of a CaSR antagonist, NPS2143, on the vascular remodeling by autophagy modulation under hypoxia. Methods: Hypoxic rat PAH model were simulated in vivo. Meanwhile, mean Pulmonary Artery Pressure (mPAP) was measured while RVI, WT%, and WA% indices were calculated. Immunohistochemistry and Western blot were used to detect phenotypic switching and cell proliferation in pulmonary arteriole. Cell viability was determined in vitro by CCK8 and cell cycle. Cell proliferation, phenotypic switching, autophagy level and PI3K/Akt/mTOR pathways were investigated in human PASMCs through mRNA or Western blot methods. Results: Rats with hypoxic-induced PAH had an increased mPAP, RVI, WT% and WA%. Moreover, expression of CaSR was significantly increased, followed by activation of autophagy (increased LC3b and decreased p62), phenotypic switching of PASMCs (reduced calponin, SMA-a and increased OPN) and pulmonary vascular remodeling. However, NPS2143 weakened these hypoxic effects. The results using hypoxic-induced human PASMCs confirmed that NPS2143 suppressed autophagy and reversed phenotypic switching in vitro by inhibiting PI3K/Akt/mTOR pathways. Conclusions: Our study demonstrates that NPS2143 was conducive to inhibit the proliferation and reverse phenotypic switching of PASMCs by regulating autophagy levels in HPH and vascular remodeling.

scholarly journals Notch4 mediates vascular remodeling via ERK/JNK/P38 MAPK signaling pathways in hypoxic pulmonary hypertension

2022 ◽  
Vol 23 (1) ◽  
Author(s):  
Mingzhou Guo ◽  
Mengzhe Zhang ◽  
Xiaopei Cao ◽  
Xiaoyu Fang ◽  
Ke Li ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Right Ventricular ◽  
Signaling Pathways ◽  
P38 Mapk ◽  
Vascular Remodeling ◽  
Cell Surface Receptor ◽  
Cell Counting ◽  
Pulmonary Vascular Remodeling ◽  
Hypoxic Pulmonary Hypertension ◽  
And Migration

Abstract Background Hypoxic pulmonary hypertension (HPH) is a chronic progressive advanced disorder pathologically characterized by pulmonary vascular remodeling. Notch4 as a cell surface receptor is critical for vascular development. However, little is known about the role and mechanism of Notch4 in the development of hypoxic vascular remodeling. Methods Lung tissue samples were collected to detect the expression of Notch4 from patients with HPH and matched controls. Human pulmonary artery smooth muscle cells (HPASMCs) were cultured in hypoxic and normoxic conditions. Real-time quantitative PCR and western blotting were used to examine the mRNA and protein levels of Notch4. HPASMCs were transfected with small interference RNA (siRNA) against Notch4 or Notch4 overexpression plasmid, respectively. Cell viability, cell proliferation, apoptosis, and migration were assessed using Cell Counting Kit-8, Edu, Annexin-V/PI, and Transwell assay. The interaction between Notch4 and ERK, JNK, P38 MAPK were analyzed by co-immunoprecipitation. Adeno-associated virus 1-mediated siRNA against Notch4 (AAV1-si-Notch4) was injected into the airways of hypoxic rats. Right ventricular systolic pressure (RVSP), right ventricular hypertrophy and pulmonary vascular remodeling were evaluated. Results In this study, we demonstrate that Notch4 is highly expressed in the media of pulmonary vascular and is upregulated in lung tissues from patients with HPH and HPH rats compared with control groups. In vitro, hypoxia induces the high expression of Delta-4 and Notch4 in HPASMCs. The increased expression of Notch4 promotes HPASMCs proliferation and migration and inhibits cells apoptosis via ERK, JNK, P38 signaling pathways. Furthermore, co-immunoprecipitation result elucidates the interaction between Notch4 and ERK/JNK/P38. In vivo, silencing Notch4 partly abolished the increase in RVSP and pulmonary vascular remodeling caused by hypoxia in HPH rats. Conclusions These findings reveal an important role of the Notch4-ERK/JNK/P38 MAPK axis in hypoxic pulmonary remodeling and provide a potential therapeutic target for patients with HPH.

scholarly journals The six-transmembrane protein Stamp2 ameliorates pulmonary vascular remodeling and pulmonary hypertension in mice

2020 ◽  
Vol 115 (6) ◽  
Author(s):  
Mehreen Batool ◽  
Eva M. Berghausen ◽  
Mario Zierden ◽  
Marius Vantler ◽  
Ralph T. Schermuly ◽  
...  
Keyword(s):  
Vascular Remodeling ◽  
Neutralizing Antibodies ◽  
Transmembrane Protein ◽  
Pulmonary Vascular Remodeling ◽  
Pulmonary Arterial ◽  
Pulmonary Arterial Smooth Muscle ◽  
And Migration ◽  
Deficient Mice ◽  
Proliferation And Migration

AbstractSix-transmembrane protein of prostate (Stamp2) protects from diabetes and atherosclerosis in mice via anti-inflammatory mechanisms. As chronic inflammation is a hallmark of pulmonary arterial hypertension (PAH), we investigated the role of Stamp2. Stamp2 expression was substantially reduced in the lung of humans with idiopathic PAH, as well as in experimental PAH. In Stamp2-deficient mice, hypoxia modestly aggravated pulmonary vascular remodeling and right ventricular pressure compared to WT. As endothelial cell (EC) and pulmonary arterial smooth muscle cell (PASMC) phenotypes drive remodeling in PAH, we explored the role of Stamp2. Knock-down of Stamp2 in human EC neither affected apoptosis, viability, nor release of IL-6. Moreover, Stamp2 deficiency in primary PASMC did not alter mitogenic or migratory properties. As Stamp2 deficiency augmented expression of inflammatory cytokines and numbers of CD68-positive cells in the lung, actions of Stamp2 in macrophages may drive vascular remodeling. Thus, PASMC responses were assessed following treatment with conditioned media of primary Stamp2−/− or WT macrophages. Stamp2−/− supernatants induced PASMC proliferation and migration stronger compared to WT. A cytokine array revealed CXCL12, MCP-1 and IL-6 as most relevant candidates. Experiments with neutralizing antibodies confirmed the role of these cytokines in driving Stamp2’s responses. In conclusion, Stamp2 deficiency aggravates pulmonary vascular remodeling via cross-talk between macrophages and PASMC. Despite a substantial pro-inflammatory response, the hemodynamic effect of Stamp2 deficiency is modest suggesting that additional mechanisms apart from inflammation are necessary to induce severe PAH.

Fluorofenidone attenuates vascular remodeling in hypoxia-induced pulmonary hypertension of rats

2014 ◽  
Vol 92 (1) ◽  
pp. 58-69 ◽  
Author(s):  
Xian-Wei Li ◽  
Jie Du ◽  
Gao-Yun Hu ◽  
Chang-Ping Hu ◽  
Dai Li ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Vascular Remodeling ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Brdu Incorporation ◽  
Pulmonary Vascular Remodeling ◽  
Collagen Iii ◽  
Pulmonary Arterial

Fluorofenidone (AKF-PD) is a novel pyridone derivate that targets transforming growth factor-β1 (TGF-β1) signaling. Previous studies have proven that AKF-PD functions as an antifibrotic agent in pulmonary fibrosis and renal fibrosis models. Activated TGF-β1 signaling is thought to be a major feature of pulmonary hypertension (PH). TGF-β1 exerts powerful pro-proliferation effects on pulmonary arterial smooth muscle cells (PASMCs), and hence, prompts vascular remodeling. This study is designed to investigate the effect of AKF-PD on vascular remodeling in a rat model of hypoxia-induced PH. PH was induced in rats by 4 weeks of hypoxia. The expression of TGF-β1, collagen I, and collagen III was analyzed by ELISA, immunohistochemistry, real-time PCR, or Western blot. Proliferation of cultured PASMCs was determined by the BrdU incorporation method and flow cytometry. The results showed that AKF-PD treatment (0.5 or 1.0 g·(kg body mass)·d−1) for 4 weeks attenuated pulmonary vascular remodeling and improved homodynamic parameters. TGF-β1 level was significantly down-regulated by AKF-PD both in vivo and in vitro. Furthermore, hypoxia- and TGF-β1-induced PASMC proliferation and collagen expression were both significantly suppressed by AKF-PD. These results suggest that AKF-PD ameliorates the progression of PH induced by hypoxia in rats through its regulation of TGF-β1 expression, PASMC proliferation, and the extracellular matrix.

PAF antagonists inhibit pulmonary vascular remodeling induced by hypobaric hypoxia in rats

1992 ◽  
Vol 73 (3) ◽  
pp. 1084-1092 ◽  
Author(s):  
S. Ono ◽  
J. Y. Westcott ◽  
N. F. Voelkel
Keyword(s):  
Pulmonary Hypertension ◽  
Vascular Remodeling ◽  
Chronic Hypoxia ◽  
Pressor Response ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Hypoxic Exposure ◽  
Pulmonary Vascular Remodeling ◽  
Paf Antagonists ◽  
Isolated Lungs

Chronic hypoxia causes pulmonary hypertension and pulmonary vascular remodeling in rats. Because platelet-activating factor (PAF) levels increase in lung lavage fluid and in plasma from chronically hypoxic rats, we examined the effect of two specific, structurally unrelated PAF antagonists, WEB 2170 and BN 50739, on hypoxia-induced pulmonary vascular remodeling. Treatment with either agent reduced hypoxia-induced pulmonary hypertension and right ventricular hypertrophy at 3 wk of hypoxic exposure (simulated altitude 5,100 m) but did not affect cobalt (CoCl2)-induced pulmonary hypertension. The PAF antagonists had no effect on the hematocrit of normoxic or chronically hypoxic rats or CoCl2-treated rats. Hypoxia-induced pulmonary hypertension was associated with an increase in the vessel wall thickness of the muscular arteries and reduction in the number of peripheral arterioles. In WEB 2170-treated rats, these changes were significantly less severe than those observed in untreated chronically hypoxic rats. PAF receptor blockade had no acute hemodynamic effects; i.e., it did not affect pulmonary arterial pressure or cardiac output nor did it affect the magnitude of acute hypoxic pulmonary vasoconstriction in awake normoxic or chronically hypoxic rats. Isolated lungs from chronically hypoxic rats showed a pressor response to the chemotactic tripeptide N-formyl-Met-Leu-Phe (fMLP) and an increase in the number of leukocytes lavaged from the pulmonary circulation. In vivo treatment with WEB 2170 significantly reduced the fMLP-induced pressor response compared with that observed in isolated lungs from untreated chronically hypoxic rats. These results suggest that PAF contributes to the development of chronic pulmonary hypertension induced by chronic hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

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