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. 2008 Jun;89(3):201–208. doi: 10.1111/j.1365-2613.2008.00585.x

Inhalation of Stachybotrys chartarum causes pulmonary arterial hypertension in mice

Eri Ochiai *, Katsuhiko Kamei *, Akira Watanabe *,†, Masaru Nagayoshi *,‡, Yuji Tada ‡, Tetsutaro Nagaoka §, Koichi Sato §, Ayaka Sato *, Kazutoshi Shibuya
PMCID: PMC2525769  PMID: 18460072

Abstract

Inhalation of Stachybotrys chartarum, a ubiquitous fungus in our living environment, has been suspected as a cause of acute idiopathic pulmonary haemorrhage in infants, but its relation to human diseases is not yet known. The aim of present study was to investigate the effect of repeated intratracheal injection of the fungus into mice, paying special attention to the pulmonary vascular system. Spores of S. chartarum were injected into the trachea of mice from 6 to 18 times over 4–12 weeks, and the lungs were examined by histopathology, morphometrics and haemodynamics. When 1 × 104 spores/mouse were injected, histopathological examination showed the development of pulmonary arterial hypertension (PAH). Symmetrical thickening of the intima and media of the pulmonary arterial walls was seen after six injections over 4 weeks. Right ventricular hypertrophy was also evident after 12 injections. PAH was confirmed by the elevation of right ventricular systolic pressure (20.1 ± 5.7 mmHg in the injected group vs. 12.0 ± 2.4 mmHg in the control group, P < 0.01). This study showed that the inhalation of S. chartarum caused PAH in mice, suggesting a potential of S. chartarum as a cause of human health problem such as PAH.

Keywords: fungi, intratracheal injection, mouse, pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a disease characterized by sustained vasoconstriction and remodelling of pulmonary arterial wall, leading to right ventricular failure and death. Although various diseases cause PAH, there are some cases in which the aetiology remains unknown, and these cases are classified as idiopathic pulmonary arterial hypertension (IPAH). The incidence of IPAH is about 1–2 cases per million per year (Gaine & Rubin 1998). Patients spend years before being diagnosed because subjective symptoms are not clear until the late stage of the disease. Although the introduction of new drugs such as bosentan, an endothelin receptor antagonist, and prostacyclin has improved prognosis (McLaughlin et al. 2002, 2005), the understanding of the precise mechanism of PAH is still required for the further development of new, more effective therapy.

Stachybotrys chartarum is a dematiaceous fungus frequently isolated in many countries from the environment particularly in water-damaged buildings and cellulose-based materials such as wallpaper and gypsum board (Samson et al. 2004). The inhalation of S. chartarum has been suggested as a cause of acute idiopathic pulmonary haemorrhage in infants (Centers for Disease Control and Prevention 1997, 2000), but the significance of S. chartarum as a causative agent of human disease is not clear, except in mycotoxicosis.

We previously reported that single or repeated intratracheal injection of spores of S. chartarum into mice for up to 3 weeks caused a unique inflammation in the lung (Ochiai et al. 2005). A single injection of spores (1 × 104 spores/mouse) induced infiltration of inflammatory cells into pulmonary alveoli after 24 h, which then subsided within 7 days. When the injection was repeated twice weekly for 3 weeks (1 × 105 spores/mouse for each injection), segmented leucocytes infiltrated into the perivascular space, although no spores were observed around the arteries. The spores did not germinate, and were gradually destroyed and cleared from the lung without causing infection. Considering the unique histopathological changes, we suspected that longer exposure of the fungus by intratracheal injection would lead to more serious changes in the pulmonary vascular system. The purpose of this study was to explore the influence of longer repeated inhalations of S. chartarum in mice, especially on pulmonary vascular system.

Methods

Fungal preparation

Stachybotrys chartarum strain IFM53637 was used throughout the study. The fungus was isolated from house dust and has been stored in our institute. The fungus was cultured on potato dextrose agar (Difco Laboratories, Detroit, MI, USA) slants for 3 weeks at 25 °C. Spores were collected in RPMI1640 medium (Sigma, St. Louis, MO, USA), and the concentration was adjusted to 4 × 103, 4 × 104 and 4 × 105 spores/ml.

Intratracheal injection

Six-week-old male ddY mice (Tokyo Laboratory Animals Science, Tokyo, Japan) were used. Their mean weight was 27.4 ± 1.21 g. Mice were divided into three groups depending on the number of spores to be injected, and were anaesthetized with an intraperitoneal injection of ketamine (65 mg/kg) and xylazine (13 mg/kg) mixture. The mice were placed in a supine position, and were intratracheally injected with 24 G intravascular catheter (Insyte-W; Becton Dickinson, Sandy, UT, USA). The spore suspension (25 μl/mouse) was injected through the catheter into the trachea. To evaluate the effect of the number of the spores, we injected 1 × 102, 1 × 103 or 1 × 104 spores into each mouse at 4–5 day intervals for 8 weeks; i.e., 12 times during 8 weeks (8-week exposure groups, n = 6, 6, and 10).

Based on the preliminary study, experiments were performed to histopathologically analyse the sequential effect of injection of 1 × 104 spores/mouse over a longer period. In one group, injection was repeated for up to 6 weeks, and the mice were sacrificed 4 days after the sixth (n = 2), eighth (n = 3), or tenth (n = 3) injection. In another group, injection was repeated 18 times during 12 weeks (12-week exposure group, n = 11).

In each experiment, mice in the control group (n = 6) received intratracheal injection of RPMI 1640 medium only. The body weights of the mice were examined, and they were then sacrificed 1 day after the last injection unless otherwise specified.

Similarly, for the experiment for the haemodynamic analysis, mice were given 1 × 104 spores/mouse 18 times during 12 weeks (n = 11) and control mice received RPMI1640 only (n = 13).

All mice were cared for in accordance with the rules and regulations set out by the Prime Minister's Office of Japan. Animal protocols were approved by the Special Committee on Animal Welfare of Chiba University.

Histopathology and morphometric analysis of pulmonary arteries, right ventricular hypertrophy

Mice were sacrificed by ether overdose on the day following the last spore injection. Lung, liver, kidney and spleen were removed and fixed with formaldehyde, embedded in paraffin, cut into 3-μm-thick sections, and stained with haematoxylin and eosin for histopathological examination. Elastica van Gieson or elastica Masson's double staining was also used on some samples.

To determine the luminal stenosis of pulmonary arteries, 12-week exposure group mice that had received 1 × 104 spores/mouse (n = 4) and control mice (n = 4) were examined. From the 12-week exposure group, four mice with pulmonary arterial lesions were chosen at random and used for the analysis. Pathological specimens taken from each pulmonary lobe, i.e. five specimens in one mouse, were examined. The diameter of each pulmonary artery was measured. The total pulmonary artery area and lumen area were calculated as the areas within the outer and inner perimeters, respectively, and the degree of stenosis was expressed as stenotic index. Stenotic index was calculated as a (1-lumen area of pulmonary artery/total pulmonary artery area) × 100. Stenosis of pulmonary arteries was classified into three groups by the degree of luminal stenosis, i.e. stenotic index: no evidence of neointimal formation; neointimal formation with partial luminal stenosis (<50%); and neointimal formation with luminal stenosis (≥50%) (Oka et al. 2007). All images were photographed with AxioVision (Carl Zeiss, Thornwood, NY) and analysed with Imagej 1.36b software (National Institutes of Health, Bethesda, MD, USA).

To evaluate the presence of PAH, hearts were dissected, and an index of right ventricular (RV) hypertrophy was calculated as the ratio of wet weight of the RV wall to wet weight of the left ventricular wall plus septum (LV + S).

Haemodynamic measurements

Right ventricular systolic pressure (RVSP) as well as left ventricular systolic pressure (LVSP) was measured as previously described (Fagan et al. 1999). Briefly, 4 days after the last injection of the fungus, mice were anaesthetized by intraperitoneal injection of tribromoethanol (400 mg/kg) and placed in a supine position while breathing spontaneously (Meyer & Fish 2005). After calibration of the zero point of the pressure transducer to the mid-antero-posterior diameter of the chest, a 26-G needle was introduced percutaneously into the thorax via a subxyphloid approach. RVSP, LVSP and heart rate were measured with a pressure transducer (MPU-0.5, P-200T; Nihon Koden, Tokyo) and recorded. If the heart rate fell below 300 beats/min, it was assumed that the level of anaesthesia was inhibiting cardiac function, and those measurements were excluded from analysis. After the measurement, mice were sacrificed and the lungs were removed for histopathologic examination.

Statistical analyses

Data were given as mean ± SD. Statistical analyses were performed by non-paired t-tests. Differences were considered significant at P < 0.05.

Results

Histopathology

Histopathological examination showed that, as in our previous study (Ochiai et al. 2005), a mild inflammatory cell infiltration was present in pulmonary alveoli soon after the intratracheal injection of spores. As the injections were repeated, the alveolar infiltrate subsided while a new infiltrate appeared in the perivascular space. Then, in the 1 × 104 injection group, substantial thickening in the pulmonary arterial wall developed as the perivascular inflammation gradually subsided. This pulmonary arterial thickening became evident after six injections (4 weeks). As spore injection was repeated, the pulmonary arterial thickening worsened both in incidence and severity. Diffuse symmetric thickening of the pulmonary artery intima and media was seen in four of 10 mice (40.0%) after 12 injections (8 weeks), and in seven of 11 mice (63.3%) after 18 injections (12 weeks) in the 1 × 104 injection group (Figure 1a,b). The thickened intima and media were accompanied by proliferation of myointimal and smooth muscle cells, respectively (Figure 1c,d). The vascular lesions developed predominantly in the pulmonary arteries of smaller diameter, and were found equally in all pulmonary lobes. The development of arterial changes was heterogeneous, and various stages of the changes were seen in each mouse, i.e., some arteries were totally occluded whereas others remained apparently normal. No venous changes were present.

Figure 1.

Figure 1

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Histopathological findings in the lungs of a mouse from the 12-week exposure group. Mice were intratracheally injected with spores of Stachybotrys chartarum at 1 × 104 spores/mouse (18 times), and were sacrificed 1 day after the last injection. (a) Pulmonary arteries with thickened walls were diffusely distributed in the lung (haematoxylin and eosin stain). Arrows indicate representative pulmonary arteries with stenotic changes. (b) Symmetrical thickening of the intima and media of the vascular wall is demonstrated at the periphery of the pulmonary arteries (elastica Masson's double stain). (c) Intima and media thickening of the vascular wall caused pulmonary artery stenosis (elastica Masson's double stain). (d) Myointimal cell proliferation in the intima caused symmetric thickening of the arterial wall and extensive stenosis (haematoxylin and eosin stain). Scale bars, 500 μm (a), 100 μm (b), 10 μm (c, d).

Luminal stenosis of pulmonary arteries and RV/(LV + S) ratio

Significant increase of stenotic index was observed in S. chartarum exposure group when compared with control (Figure 2a–c). Analysis of pulmonary arteries in S. chartarum exposure group mice showed that 58.4% of the arteries had the neointimal formation with a high degree of luminal stenosis (stenotic index higher than 50%) (Figure 2c,d). The greatest pulmonary arterial changes corresponded to grade 3 of the Heath–Edwards classification (Heath & Edwards 1958). The RV/(LV + S) ratio increased significantly in the 12-week exposure group, indicating the development of right ventricular hypertrophy (P < 0.05; 0.44 ± 0.06 in the 12-week exposure group vs. 0.37 ± 0.03 in the control group). The body weight of mice was significantly decreased in the 8- and 12-week exposure groups (P < 0.01, 42.8 ± 1.67 in the 8-week exposure group vs. 46.9 ± 1.94 in the control group; P < 0.05, 45.6 ± 4.04 in the 12-week exposure group vs. 50.9 ± 5.22 in the control group) (Table 1).

Figure 2.

Figure 2

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Morphometric analysis of luminal stenosis of pulmonary arteries. (a, b) Stenotic index [(1 − luminal area of pulmonary artery/total pulmonary artery area) × 100] vs. diameter of pulmonary arteries. (c) Diameter of pulmonary arteries and degree of stenosis. *P < 0.0001 vs. control. (d) Percentage of pulmonary arteries classified by the neointimal proliferative lesions and the degree of stenosis.

Table 1.

Effects of repeated inhalation of Stachybotrys chartarum on ventricular weights in mice

8-week exposure group 12-week exposure group
Control S. chartarum Control S. chartarum
No. of mice 6 10 5 11
BW (g) 46.9 ± 1.94 42.8 ± 1.67* 50.9 ± 5.22 45.6 ± 4.04†
RV/(LV + S) 0.38 ± 0.03 0.43 ± 0.06 0.37 ± 0.03 0.44 ± 0.06†
RV/BW (×10−3) 1.00 ± 0.05 1.28 ± 0.00* 0.96 ± 0.10 1.17 ± 0.00†
(LV + S)/BW (×10−3) 2.63 ± 0.31 2.94 ± 0.00† 2.59 ± 0.16 2.57 ± 0.00
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Values are expressed as mean ± SD. BW, body weight; RV, right ventricular; LV + S, left ventricular plus septum weight.

*

P < 0.01 vs. control.

†

P < 0.05 vs. control.

Haemodynamic measurement

In the haemodynamic study, seven mice in the 12-week exposure group and eight mice in the control group showed a heart rate higher than 300 beats per min, and they were used for the analysis. Statistical analysis disclosed that RVSP was significantly higher in the S. chartarum exposure group than in the control group (20.1 ± 5.7 mmHg in the exposure group vs. 12.0 ± 2.4 mmHg in the control group; P < 0.01) (Figure 3). LVSP was not elevated (data not shown).

Figure 3.

Figure 3

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Pulmonary haemodynamics in mice. Right ventricular systolic pressure (RVSP) was measured after the 12-week exposure to RPMI1640 (n = 8) or Stachybotrys chartarum (n = 7). Repeated inhalation of S. chartarum caused an increase in RVSP. Mice with a heart rate less than 300 beats/min were excluded. Values are expressed as mean ± SD. *P < 0.01 vs. control.

As seen in our previous study, spores were seen in the lung only for a limited period after the injection, and then they gradually disappeared. When present, the spores were located inside pulmonary alveoli or perivascular space, and many of them were surrounded mostly by polymorphonuclear leucocyte or phagocytized by macrophages. No germination of spores was observed under any experimental condition. The distribution of spores and the vascular lesions had no apparent relation. No findings of vasculitis were detected.

When fewer spores such as 1 × 102 and 1 × 103 spores/mouse were given, no vascular changes developed in the lung, and cell infiltration was limited to the intra-alveolar spaces, not in the areas surrounding the pulmonary arteries.

As for the other organs, such as liver, kidney and spleen, no histopathological changes were detected regardless of the experimental conditions. No lesions suggestive of pulmonary haemorrhage such as haemosiderin accumulation in macrophages were observed in any of the experiments.

All through the experiments, only one mouse died, which was caused by asphyxia from the fungal suspension. This animal was excluded from the analysis.

Discussion

In the present study, we showed that repeated inhalation of a ubiquitous fungus, S. chartarum, caused PAH in mice. The pulmonary changes, such as thickening of the intima and media of the pulmonary arteries in the absence of any other disease known to cause chronic cor pulmonale, were close to human PAH in histopathology. To the best of our knowledge, there has been no report to show that inhalation of a fungus caused PAH in any animal.

Although there are certain differences, the histopathological findings of our model had several similarities to IPAH. Today only a few animal models of PAH are available, with most of them relying on rats as the model animal (Pullamsetti et al. 2005; Maruyama et al. 2007). In fact, making murine models of PAH has been variously tried in vain. The exception is seen in transgenic animals such as bone morphogenetic protein receptor type II (BMPR2) knockout mice (West et al. 2004) and serotonin transporter overexpressing mice (Guignabert et al. 2006), and Pneumocystis-infected mice (Swain et al. 2007). We used genetically normal mice without pre-existing disease, a uniqueness in itself.

Another uniqueness of our model is in the development of substantial neointimal changes. As indicated by Bauer et al., the development of intimal thickening of pulmonary arteries is an important pathological issue (Bauer et al. 2007). The representative rodent models of pulmonary hypertension, such as monocrotaline-induced and BMPR2 knockout models, are defective of the development of neointimal lesions (Heath 1992; West et al. 2004). In this regard, our model is closer to human IPAH when the pathological changes are compared with those seen in the previous models.

The aetiology of IPAH has been investigated vigorously, and mutations in BMPR2 gene and activin-like kinase type-1 receptor have been implicated in the familial form and some cases of the idiopathic form of PAH (Raiesdana & Loscalzo 2006). Drugs and toxins such as aminorex, fenfluramine, and toxic rapeseed oil are also known to promote PAH (Humbert et al. 2001). Recently a ‘two hit’ theory was proposed, in which IPAH is caused by genetic predisposition and/or environmental factors (Rudarakanchana et al. 2001). Nonetheless, these ‘environmental factors’ remain unknown. Our model may provide important clues to elucidate the aetiology of the disease although the information is limited to the mice.

Some studies reported endothelin-1 (ET-1) levels were increased in lung of patients with PAH and animal models of PAH (Giaid et al. 1993; Dai et al. 2004). ET-1 is a 21-amino acid peptide and acts as vasoconstrictors and mitogens. In our study, however, ET-1 immunoreactivity of the lung was not elevated in the mice that were exposed to S. chartarum (data not shown). It is not clear if this finding is specific to this model. Further investigations are under way as to the aetiology of these changes.

The increase in the RV/(LV + S) ratio and elevation of RVSP was more evident in the 12-week exposure group, which also suggests the advanced thickening in the 12-week exposure group.

The mouse we employed in this study is ddY. The ddY mouse is a closed colony strain, and it has been frequently used in various fields of research (Okuda-Ashitaka et al. 1998; Fueta et al. 2005). Rosenblum Lichtenstein et al. (2006) reported that the cytokine production profile in bronchoalveolar lavage after the tracheal injection of S. chartarum differed slightly according to the mouse strain, but did not refer to the development of PAH. Although the development of PAH seen in our study may also be affected by the strain of the mouse, similar changes as seen in our model can be expected to be induced in other strain of mice. Actually, we have confirmed the development of similar lesions in ICR mice when S. chartarum was injected (data not shown).

The fact that the inhalation of an airborne ubiquitous fungus caused PAH is of considerable significance. The frequently used animal model of human IPAH using genetically normal animals is that of rats treated with monocrotaline, a pyrrolizidine alkaloid extracted from seeds of Crotalaria spectabilis (Marsboom & Janssens 2004). In that model, rats are given monocrotaline by subcutaneous or intraperitoneal injection or by gavage, all of which are unlikely to occur in humans. In addition, the monocrotaline rat does not develop neointimal lesions. In contrast, S. chartarum is a common fungus, and repeated exposure may happen to any animal or even to humans in the daily life.

Whether similar exposure to S. chartarum can occur in humans is an issue of paramount importance. In general, S. chartarum comprises only a small part of the indoor air fungal population. However, the concentration of fungi in the air is known to increase substantially depending on environmental factors, such as temperature, humidity (Shelton et al. 2002). In fact, Kuhn et al. reported that the indoor concentration of Stachybotrys spp. reached a very high level, i.e. 1 × 106 spores/m3 (Kuhn et al. 2005). This fact indicates that numerous spores of the fungus can be present in the air under favourable conditions, and that, as a consequence, a large number of spores could be repeatedly inhaled on a daily basis. Although the number of inhaled spores cannot be directly compared between humans and mice, we suspect that long-term, continuous exposure in houses could pose a serious threat even in humans.

The mechanism of the development of PAH in this model is yet to be understood. One possibility is that some active substances made by the fungus might be related to the development of PAH. Of particular interest was the fact that the spores did not accumulate around the arteries, although perivascular inflammation preceded vascular wall changes. The fungi may have worked indirectly on the development of arterial changes by releasing active substances in the lung. Stachybotrys chartarum is known for its abundant production of various mycotoxins, particularly macrocyclic trichothecenes such as satratoxins, roridins and verrucarins (Cole et al. 2003), thereby causing serious mycotoxicosis in humans and animals when ingested (Sorenson et al. 1987; Miller 1992). Considering the strong biological activities of mycotoxins, some of those of this fungus, including trichothecene mycotoxins, might play a certain role. Analysis of the active components of the fungus and their functions is now under way.

This is the first report to show that the repeated intratracheal injection of spores of S. chartarum caused PAH in mice. Although the relationship between S. chartarum inhalation and the development of human IPAH is not clear, the high reproducibility of the vascular changes seen in our model should receive serious attention in terms of the implication for human diseases.

Acknowledgments

We thank Dr. Yoshitsugu Sugiura (Public Health Research Institute of Kobe City, Japan) for his generous gift of the S. chartarum isolate. We also appreciate the valuable suggestions by Dr Masatoshi Imamura (Tokyo Medical and Dental University, Japan).

This study was partly supported by Research on Measures for Intractable Diseases (grant number 17243601), Health and Labour Sciences Research Grants from the Ministry of Health, Labour and Welfare.

References

  1. Bauer NR, Moore TM, McMurtry IF. Rodent models of PAH: are we there yet? Am. J. Physiol. Lung Cell Mol. Physiol. 2007;293:L580–L582. doi: 10.1152/ajplung.00281.2007. [DOI] [PubMed] [Google Scholar]
  2. Centers for Disease Control and Prevention. Update: pulmonary hemorrhage/hemosiderosis among infants–Cleveland, Ohio, 1993–1996. Morb. Mortal. Wkly Rep. 1997;46:33–35. [PubMed] [Google Scholar]
  3. Centers for Disease Control and Prevention. Update: pulmonary hemorrhage/hemosiderosis among infants–Cleveland, Ohio, 1993–1996. Morb. Mortal. Wkly Rep. 2000;49:180–184. Erratum in: (2000) Morb. Mortal. Wkly. Rep.49, 213. [PubMed] [Google Scholar]
  4. Cole RJ, Jarvis BB, Schweikert MA. Handbook of Secondary Fungal Metabolites. Vol. 3. London: Academic Press; 2003. [Google Scholar]
  5. Dai ZK, Tan MS, Chai CY, et al. Upregulation of endothelial nitric oxide synthase and endothelin-1 in pulmonary hypertension secondary to heart failure in aorta-banded rats. Pediatr. Pulmonol. 2004;37:249–256. doi: 10.1002/ppul.10413. [DOI] [PubMed] [Google Scholar]
  6. Fagan KA, Fouty BW, Tyler RC, et al. The pulmonary circulation of homozygous or heterozygous eNOS-null mice is hyperresponsive to mild hypoxia. J. Clin. Invest. 1999;103:291–299. doi: 10.1172/JCI3862. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Fueta Y, Kunugita N, Schwarz W. Antiepileptic action induced by a combination of vigabatrin and tiagabine. Neuroscience. 2005;132:335–345. doi: 10.1016/j.neuroscience.2004.12.044. [DOI] [PubMed] [Google Scholar]
  8. Gaine SP, Rubin LJ. Primary pulmonary hypertension. Lancet. 1998;352:719–725. doi: 10.1016/S0140-6736(98)02111-4. [DOI] [PubMed] [Google Scholar]
  9. Giaid A, Yanagisawa M, Langleben D, et al. Expression of endothelin-1 in the lungs of patients with pulmonary hypertension. N. Engl. J. Med. 1993;328:1732–1739. doi: 10.1056/NEJM199306173282402. [DOI] [PubMed] [Google Scholar]
  10. Guignabert C, Izikki M, Tu LI, et al. Transgenic mice overexpressing the 5-hydroxytryptamine transporter gene in smooth muscle develop pulmonary hypertension. Circ. Res. 2006;98:1323–1330. doi: 10.1161/01.RES.0000222546.45372.a0. [DOI] [PubMed] [Google Scholar]
  11. Heath D. The rat is a poor animal model for the study of human pulmonary hypertension. Cardioscience. 1992;3:1–6. [PubMed] [Google Scholar]
  12. Heath D, Edwards JE. The pathology of hypertensive pulmonary vascular disease. Circulation. 1958;18:533–547. doi: 10.1161/01.cir.18.4.533. [DOI] [PubMed] [Google Scholar]
  13. Humbert M, Nunes H, Sitbon O, et al. Risk factors for pulmonary arterial hypertension. Clin. Chest Med. 2001;22:459–475. doi: 10.1016/s0272-5231(05)70284-7. [DOI] [PubMed] [Google Scholar]
  14. Kuhn RC, Trimble MW, Hofer V, Lee M, Nassof RS. Prevalence and airborne spore levels of Stachybotrys spp. in 200 houses with water incursions in Houston, Texas. Can. J. Microbiol. 2005;51:25–28. doi: 10.1139/w04-110. [DOI] [PubMed] [Google Scholar]
  15. Marsboom GR, Janssens SP. Models for pulmonary hypertension. Drug Discov. Today: Disease Models. 2004;1:289–296. [Google Scholar]
  16. Maruyama H, Watanabe S, Kimura T, et al. Granulocyte colony-stimulating factor prevents progression of monocrotaline-induced pulmonary arterial hypertension in rats. Circ. J. 2007;71:138–143. doi: 10.1253/circj.71.138. [DOI] [PubMed] [Google Scholar]
  17. McLaughlin VV, Shillington A, Rich S. Survival in primary pulmonary hypertension: the impact of epoprostenol therapy. Circulation. 2002;106:1477–1482. doi: 10.1161/01.cir.0000029100.82385.58. [DOI] [PubMed] [Google Scholar]
  18. McLaughlin VV, Sitbon O, Badesch DB, et al. Survival with first-line bosentan in patients with primary pulmonary hypertension. Eur. Respir. J. 2005;25:244–249. doi: 10.1183/09031936.05.00054804. [DOI] [PubMed] [Google Scholar]
  19. Meyer RE, Fish RE. A review of tribromoethanol anesthesia for production of genetically engineered mice and rats. Lab. Anim. 2005;34:47–52. doi: 10.1038/laban1105-47. [DOI] [PubMed] [Google Scholar]
  20. Miller JD. Fungi as contaminants in indoor air. Atmos. Environ. 1992;26A:2163–2172. [Google Scholar]
  21. Ochiai E, Kamei K, Hiroshima K, et al. The pathogenicity of Stachybotrys chartarum. Jpn. J. Med. Mycol. 2005;46:109–117. doi: 10.3314/jjmm.46.109. [DOI] [PubMed] [Google Scholar]
  22. Oka M, Homma N, Taraseviciene-Stewart L, et al. Rho kinase-mediated vasoconstriction is important in severe occlusive pulmonary arterial hypertension in rats. Circ. Res. 2007;100:923–929. doi: 10.1161/01.RES.0000261658.12024.18. [DOI] [PubMed] [Google Scholar]
  23. Okuda-Ashitaka E, Minami T, Tachibana S, et al. Nocistain, a peptide that blocks nociceptin action in pain transmission. Nature. 1998;392:286–289. doi: 10.1038/32660. [DOI] [PubMed] [Google Scholar]
  24. Pullamsetti S, Kiss L, Ghofrani HA, et al. Increased levels and reduced catabolism of asymmetric and symmetric dimethylarginines in pulmonary hypertension. FASEB J. 2005;19:1175–1177. doi: 10.1096/fj.04-3223fje. [DOI] [PubMed] [Google Scholar]
  25. Raiesdana A, Loscalzo J. Pulmonary arterial hypertension. Ann. Med. 2006;38:95–110. doi: 10.1080/07853890600622143. [DOI] [PubMed] [Google Scholar]
  26. Rosenblum Lichtenstein JH, Molina RM, Donaghey TC, Brain JD. Strain differences influence murine pulmonary responses to Stachybotrys chartarum. Am. J. Respir. Cell Mol. Biol. 2006;35:415–423. doi: 10.1165/rcmb.2005-0483OC. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Rudarakanchana N, Trembath RC, Morrell NW. New insights into the pathogenesis and treatment of primary pulmonary hypertension. Thorax. 2001;56:888–890. doi: 10.1136/thorax.56.11.888. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Samson RA, Hoekstra ES, Frisvad JC. Identification of the common food-borne fungi. In: Samson RA, Hoekstra ES, Frisvad JC, editors. Introduction to Food- and Airborne Fungi. 7. Utrecht: Centraalbureau voor Schimmelcultures; 2004. pp. 258–259. [Google Scholar]
  29. Shelton BG, Kirkland KH, Flanders WD, Morris GK. Profiles of airborne fungi in buildings and outdoor environments in the United States. Appl. Environ. Microbiol. 2002;68:1743–1753. doi: 10.1128/AEM.68.4.1743-1753.2002. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Sorenson WG, Frazer DG, Jarvis BB, Simpson J, Robinson VA. Trichothecene mycotoxins in aerosolized conidia of Stachybotrys atra. Appl. Environ. Microbiol. 1987;53:1370–1375. doi: 10.1128/aem.53.6.1370-1375.1987. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Swain SD, Han S, Harmsen A, Shampeny K, Harmsen AG. Pulmonary hypertension can be a sequela of prior pneumocystis pneumonia. Am. J. Pathol. 2007;171:790–799. doi: 10.2353/ajpath.2007.070178. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. West J, Fagan K, Steudel W, et al. Pulmonary hypertension in transgenic mice expressing a dominant-negative BMPRII gene in smooth muscle. Circ. Res. 2004;94:1109–1114. doi: 10.1161/01.RES.0000126047.82846.20. [DOI] [PubMed] [Google Scholar]

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