SuHx rat model: partly reversible pulmonary hypertension and progressive intima obstruction.
de Raaf Michiel Alexander,Schalij Ingrid,Gomez-Arroyo Jose,Rol Nina,Happé Chris,de Man Frances S,Vonk-Noordegraaf Anton,Westerhof Nico,Voelkel Norbert F,Bogaard Harm Jan
The European respiratory journal
The SU5416 combined with hypoxia (SuHx) rat model features angio-obliterative pulmonary hypertension resembling human pulmonary arterial hypertension. Despite increasing use of this model, a comprehensive haemodynamic characterisation in conscious rats has not been reported. We used telemetry to characterise haemodynamic responses in SuHx rats and associated these with serial histology. Right ventricular systolic pressure (RVSP) increased to a mean±sd of 106±7 mmHg in response to SuHx and decreased but remained elevated at 72±8 mmHg upon return to normoxia. Hypoxia-only exposed rats showed a similar initial increase in RVSP, a lower maximum RVSP and near-normalisation of RVSP during subsequent normoxia. Progressive vascular remodelling consisted of a four-fold increase in intima thickness, while only minimal changes in media thickness were found. The circadian range in RVSP provided an accurate longitudinal estimate of vascular remodelling. In conclusion, in SuHx rats, re-exposure to normoxia leads to a partial decrease in pulmonary artery pressure, with persisting hypertension and pulmonary vascular remodelling characterised by progressive intima obstruction.
Carotid body inflammation and cardiorespiratory alterations in intermittent hypoxia.
Del Rio Rodrigo,Moya Esteban A,Parga María J,Madrid Carlos,Iturriaga Rodrigo
The European respiratory journal
Chronic intermittent hypoxia (CIH), a main feature of obstructive sleep apnoea (OSA), increases hypoxic ventilatory responses and elicits hypertension, partially attributed to an enhance carotid body (CB) responsiveness to hypoxia. As inflammation has been involved in CIH-induced hypertension and chemosensory potentiation, we tested whether ibuprofen may block CB chemosensory and cardiorespiratory alterations induced by CIH in a rat model of OSA. We studied the effects of ibuprofen (40 mg · kg(-1) · day(-1)) on immunohistochemical interleukin (IL)-1β and tumour necrosis factor (TNF)-α levels in the CB, the number of c-fos-positive neurons in the nucleus tractus solitarii (NTS), CB chemosensory and ventilatory responses to hypoxia, and arterial blood pressure in male rats either exposed for 21 days to 5% O(2) (12 episodes · h(-1), 8 h · day(-1)) or kept under sham condition. CIH increased CB TNF-α and IL-1β and c-fos-positive neurons in the NTS, enhanced carotid chemosensory and ventilatory hypoxic responses, and produced hypertension. Ibuprofen prevented CB cytokine overexpression and CIH-induced increases in c-fos-positive neurons in the NTS, the enhanced hypoxic ventilatory responses and hypertension, but failed to impede the CB chemosensory potentiation. Results suggest that pro-inflammatory cytokines may contribute to the CIH-induced cardiorespiratory alterations, acting at several levels of the hypoxic chemoreflex and cardiovascular control pathways.
Classical transient receptor potential channel 1 in hypoxia-induced pulmonary hypertension.
Malczyk Monika,Veith Christine,Fuchs Beate,Hofmann Katharina,Storch Ursula,Schermuly Ralph T,Witzenrath Martin,Ahlbrecht Katrin,Fecher-Trost Claudia,Flockerzi Veit,Ghofrani Hossein A,Grimminger Friedrich,Seeger Werner,Gudermann Thomas,Dietrich Alexander,Weissmann Norbert
American journal of respiratory and critical care medicine
RATIONALE:Pulmonary hypertension (PH) is a life-threatening disease, characterized by pulmonary vascular remodeling. Abnormal smooth muscle cell proliferation is a primary hallmark of chronic hypoxia-induced PH. Essential for cell growth are alterations in the intracellular Ca(2+) homeostasis. Classical transient receptor potential (TRPC) proteins have been suggested to contribute to PH development, as TRPC1 and TRPC6 are predominantly expressed in precapillary pulmonary arterial smooth muscle cells (PASMC). Studies in a TRPC6-deficient mouse model revealed an essential function of TRPC6 in acute but not in chronic hypoxia. OBJECTIVES:We aimed to identify the importance of TRPC1 in the pathogenesis of chronic hypoxia-induced PH in mice. METHODS:TRPC1 expression analysis was performed using real-time polymerase chain reaction. TRPC1 function was assessed by in vivo experiments in TRPC1(-/-) animals as well as in isolated precapillary murine PASMC after TRPC1 knockdown by TRPC1-specific small interfering RNAs. MEASUREMENTS AND MAIN RESULTS:Only TRPC1 mRNA was up-regulated under hypoxia in isolated murine PASMC (1% O2 for 72 h). Hypoxia-induced proliferation of murine PASMC was attenuated in cells treated with small interfering RNA against TRPC1 and in cells isolated from TRPC1(-/-) animals compared with untreated and wild-type cells. TRPC1(-/-) mice did not develop PH in response to chronic hypoxia (FI(O2) 0.10 for 21 d) and had less vascular muscularization but a similar degree of right ventricular hypertrophy compared with wild-type mice. CONCLUSIONS:Our results indicate an important role of TRPC1 in pulmonary vascular remodeling underlying the development of hypoxia-induced PH.
Intermittent hypoxia and stem cell implants preserve breathing capacity in a rodent model of amyotrophic lateral sclerosis.
Nichols Nicole L,Gowing Genevieve,Satriotomo Irawan,Nashold Lisa J,Dale Erica A,Suzuki Masatoshi,Avalos Pablo,Mulcrone Patrick L,McHugh Jacalyn,Svendsen Clive N,Mitchell Gordon S
American journal of respiratory and critical care medicine
RATIONALE:Amyotrophic lateral sclerosis (ALS) is a devastating motor neuron disease causing paralysis and death from respiratory failure. Strategies to preserve and/or restore respiratory function are critical for successful treatment. Although breathing capacity is maintained until late in disease progression in rodent models of familial ALS (SOD1(G93A) rats and mice), reduced numbers of phrenic motor neurons and decreased phrenic nerve activity are observed. Decreased phrenic motor output suggests imminent respiratory failure. OBJECTIVES:To preserve or restore phrenic nerve activity in SOD1(G93A) rats at disease end stage. METHODS:SOD1(G93A) rats were injected with human neural progenitor cells (hNPCs) bracketing the phrenic motor nucleus before disease onset, or exposed to acute intermittent hypoxia (AIH) at disease end stage. MEASUREMENTS AND MAIN RESULTS:The capacity to generate phrenic motor output in anesthetized rats at disease end stage was: (1) transiently restored by a single presentation of AIH; and (2) preserved ipsilateral to hNPC transplants made before disease onset. hNPC transplants improved ipsilateral phrenic motor neuron survival. CONCLUSIONS:AIH-induced respiratory plasticity and stem cell therapy have complementary translational potential to treat breathing deficits in patients with ALS.
Altered expression of platelet proteins and calpain activity mediate hypoxia-induced prothrombotic phenotype.
Tyagi Tarun,Ahmad Shadab,Gupta Neha,Sahu Anita,Ahmad Yasmin,Nair Velu,Chatterjee Tathagat,Bajaj Nitin,Sengupta Shantanu,Ganju Lilly,Singh Shashi Bala,Ashraf Mohammad Z
Oxygen-compromised environments, such as high altitude, air travel, and sports, and pathological conditions, such as solid tumors, have been suggested to be prothrombotic. Despite the indispensable role of platelets in thrombus formation, the studies linking hypoxia, platelet reactivity, and thrombus formation are limited. In the present study, platelet proteome/reactivity was analyzed to elucidate the acute hypoxia-induced prothrombotic phenotype. Rats exposed to acute simulated hypoxia (282 torr/8% oxygen) demonstrated a decreased bleeding propensity and increased platelet reactivity. Proteomic analysis of hypoxic platelets revealed 27 differentially expressed proteins, including those involved in coagulation. Among these proteins, calpain small subunit 1, a 28-kDa regulatory component for calpain function, was significantly upregulated under hypoxic conditions. Moreover, intraplatelet Ca(2+) level and platelet calpain activity were also found to be in accordance with calpain small subunit 1 expression. The inhibition of calpain activity demonstrated reversal of hypoxia-induced platelet hyperreactivity. The prothrombotic role for calpain was further confirmed by an in vivo model of hypoxia-induced thrombosis. Interestingly, patients who developed thrombosis while at extreme altitude had elevated plasma calpain activities and increased soluble P-selectin level. In summary, this study suggests that augmented calpain activity is associated with increased incidence of thrombosis under hypoxic environments.
Protective Roles of Endothelial AMP-Activated Protein Kinase Against Hypoxia-Induced Pulmonary Hypertension in Mice.
Omura Junichi,Satoh Kimio,Kikuchi Nobuhiro,Satoh Taijyu,Kurosawa Ryo,Nogi Masamichi,Otsuki Tomohiro,Kozu Katsuya,Numano Kazuhiko,Suzuki Kota,Sunamura Shinichiro,Tatebe Shunsuke,Aoki Tatsuo,Sugimura Koichiro,Miyata Satoshi,Hoshikawa Yasushi,Okada Yoshinori,Shimokawa Hiroaki
RATIONALE:Endothelial AMP-activated protein kinase (AMPK) plays an important role for vascular homeostasis, and its role is impaired by vascular inflammation. However, the role of endothelial AMPK in the pathogenesis of pulmonary arterial hypertension (PAH) remains to be elucidated. OBJECTIVE:To determine the role of endothelial AMPK in the development of PAH. METHODS AND RESULTS:Immunostaining showed that endothelial AMPK is downregulated in the pulmonary arteries of patients with PAH and hypoxia mouse model of pulmonary hypertension (PH). To elucidate the role of endothelial AMPK in PH, we used endothelial-specific AMPK-knockout mice (eAMPK(-/-)), which were exposed to hypoxia. Under normoxic condition, eAMPK(-/-) mice showed the normal morphology of pulmonary arteries compared with littermate controls (eAMPK(flox/flox)). In contrast, development of hypoxia-induced PH was accelerated in eAMPK(-/-) mice compared with controls. Furthermore, the exacerbation of PH in eAMPK(-/-) mice was accompanied by reduced endothelial function, upregulation of growth factors, and increased proliferation of pulmonary artery smooth muscle cells. Importantly, conditioned medium from endothelial cells promoted pulmonary artery smooth muscle cell proliferation, which was further enhanced by the treatment with AMPK inhibitor. Serum levels of inflammatory cytokines, including tumor necrosis factor-α and interferon-γ were significantly increased in patients with PAH compared with healthy controls. Consistently, endothelial AMPK and cell proliferation were significantly reduced by the treatment with serum from patients with PAH compared with controls. Importantly, long-term treatment with metformin, an AMPK activator, significantly attenuated hypoxia-induced PH in mice. CONCLUSIONS:These results indicate that endothelial AMPK is a novel therapeutic target for the treatment of PAH.
Hypoxia enhances CD8 T2 cell-dependent airway hyperresponsiveness and inflammation through hypoxia-inducible factor 1α.
Ning Fangkun,Takeda Katsuyuki,Schedel Michaela,Domenico Joanne,Joetham Anthony,Gelfand Erwin W
The Journal of allergy and clinical immunology
BACKGROUND:CD8 type 2 cytotoxic T (T2) cells undergo transcriptional reprogramming to IL-13 production in the presence of IL-4 to become potent, steroid-insensitive, pathogenic effector cells in asthmatic patients and in mice in a model of experimental asthma. However, no studies have described the effects of hypoxia exposure on T2 cell differentiation. OBJECTIVE:We determined the effects of hypoxia exposure on IL-13-producing CD8 T2 cells. METHODS:CD8 transgenic OT-1 cells differentiated with IL-2 and IL-4 (T2 cells) were exposed to normoxia (21% oxygen) or hypoxia (3% oxygen), and IL-13 production in vitro was monitored. After differentiation under these conditions, cells were adoptively transferred into CD8-deficient mice, and lung allergic responses, including airway hyperresponsiveness to inhaled methacholine, were assessed. The effects of pharmacologic inhibitors of hypoxia-inducible factor (HIF) 1α and HIF-2α were determined, as were responses in HIF-1α-deficient OT-1 cells. RESULTS:Under hypoxic conditioning, CD8 T2 cell differentiation was significantly enhanced, with increased numbers of IL-13 T cells and increased production of IL-13 in vitro. Adoptive transfer of T2 cells differentiated under hypoxic conditioning restored lung allergic responses in sensitized and challenged CD8-deficient recipients to a greater degree than seen in recipients of T2 cells differentiated under normoxic conditioning. Pharmacologic inhibition of HIF-1α or genetic manipulation to reduce HIF-1α expression reduced the hypoxia-enhanced differentiation of T2 cells, IL-13 production, and the capacity of transferred cells to restore lung allergic responses in vivo. IL-4-dependent, hypoxia-mediated increases in HIF-1α and T2 cell differentiation were shown to be mediated through activation of Janus kinase 1/3 and GATA-3. CONCLUSIONS:Hypoxia enhances CD8 T2 cell-dependent airway hyperresponsiveness and inflammation through HIF-1α activation. These findings coupled with the known insensitivity of CD8 T cells to corticosteroids suggests that activation of the IL-4-HIF-1α-IL-13 axis might play a role in the development of steroid-refractory asthma.
Intermittent hypoxia alters gut microbiota diversity in a mouse model of sleep apnoea.
Moreno-Indias Isabel,Torres Marta,Montserrat Josep M,Sanchez-Alcoholado Lidia,Cardona Fernando,Tinahones Francisco J,Gozal David,Poroyko Valeryi A,Navajas Daniel,Queipo-Ortuño Maria I,Farré Ramon
The European respiratory journal
We assessed whether intermittent hypoxia, which emulates one of the hallmarks of obstructive sleep apnoea (OSA), leads to altered faecal microbiome in a murine model. In vivo partial pressure of oxygen was measured in colonic faeces during intermittent hypoxia in four anesthetised mice. 10 mice were subjected to a pattern of chronic intermittent hypoxia (20 s at 5% O2 and 40 s at room air for 6 h·day(-1)) for 6 weeks and 10 mice served as normoxic controls. Faecal samples were obtained and microbiome composition was determined by 16S rRNA pyrosequencing and bioinformatic analysis by Quantitative Insights into Microbial Ecology. Intermittent hypoxia exposures translated into hypoxia/re-oxygenation patterns in the faeces proximal to the bowel epithelium (<200 μm). A significant effect of intermittent hypoxia on global microbial community structure was found. Intermittent hypoxia increased the α-diversity (Shannon index, p<0.05) and induced a change in the gut microbiota (ANOSIM analysis of β-diversity, p<0.05). Specifically, intermittent hypoxia-exposed mice showed a higher abundance of Firmicutes and a smaller abundance of Bacteroidetes and Proteobacteria phyla than controls. Faecal microbiota composition and diversity are altered as a result of intermittent hypoxia realistically mimicking OSA, suggesting the possibility that physiological interplays between host and gut microbiota could be deregulated in OSA.