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J A Whitsett

Publications and source records attributed to J A Whitsett.

At least 19 recordsLinked to original sources
PubMed2006

Skeletal demineralization and fractures caused by fetal magnesium toxicity.

Two surviving female infants, born from a triplet pregnancy at 30 weeks gestation, were noted to have severe osteopenia and multiple fractures diagnosed at 20 days of age. Their mother had been treated for preterm labor with intravenous magnesium sulfate from week 22 until their birth at 30 weeks gestation. At birth, the triplets exhibited craniotabes with enlarged fontanelles and sutures. All developed Respiratory Distress Syndrome (RDS) and the two surviving infants required prolonged respiratory support. Serum calcium and phosphate levels were normal and alkaline phosphatase levels were increased. The infants were treated with supplements of calcium and phosphorous, with resultant healing of the multiple fractures without deformity. Fetal magnesium toxicity impairs bone mineralization and can lead to serious bone demineralization that may cause fractures in the newborn period that complicate recovery from respiratory disease. Early recognition and treatment may minimize complications related to osteopenia caused by fetal magnesium toxicity.

Adult↗
PubMed2005

Stage-specific regulation of respiratory epithelial cell differentiation by Foxa1.

Foxa1 is a member of the winged helix family of transcription factors that is expressed in epithelial cells of the conducting airways and in alveolar type II cells of the lung. To determine the role of Foxa1 during lung morphogenesis, histology and gene expression were assessed in lungs from Foxa1-/- gene-targeted mice from embryonic day (E) 16.5 to postnatal day (PN) 13. Deletion of Foxa1 perturbed maturation of the respiratory epithelium at precise times during lung morphogenesis. While dilatation of peripheral lung saccules was delayed in Foxa1-/- mice at E16.5, sacculation was unperturbed later in development (E17.5-E18.5). At PN5, alveolarization was markedly delayed in Foxa1-/- mice; however, by PN13 lung histology was comparable to wild-type controls. Clara cell secretory protein (CCSP), prosurfactant protein (SP)-C, and SP-B protein content and immunostaining were decreased in Foxa1-/- mice between E16.5 and E18.5 but normalized after birth. Timing and sites of expression of thyroid transcription factor-1, Foxj1, and beta-tubulin were unaltered in lungs of Foxa1-/- mice. In vitro, Foxa1 regulated the activity of CCSP and SP-A, SP-B, SP-C, and SP-D promoters as assessed by luciferase reporter assays in HeLa, H441, and MLE15 cells. Although Foxa1 regulates respiratory epithelial differentiation and structural maturation of the lung at precise developmental periods, the delay in maturation is subsequently compensated at times to enable respiratory function and restore normal lung structure after birth.

Animals↗
PubMed2004

Transient induction of TGF-alpha disrupts lung morphogenesis, causing pulmonary disease in adulthood.

Clinical studies have associated increased transforming growth factor (TGF)-alpha and EGF receptor with lung remodeling in diseases including bronchopulmonary dysplasia (BPD). BPD is characterized by disrupted alveolar and vascular morphogenesis, inflammation, and remodeling. To determine whether transient increases in TGF-alpha are sufficient to disrupt postnatal lung morphogenesis, we utilized neonatal transgenic mice conditionally expressing TGF-alpha. Expression of TGF-alpha from postnatal days 3 to 5 disrupted postnatal alveologenesis, causing permanent enlargement of distal air spaces in neonatal and adult mice. Lung volume-to-body weight ratios and lung compliance were increased in adult TGF-alpha transgenic mice, whereas tissue and airway elastance were reduced. Elastin fibers in the alveolar septae were fragmented and disorganized. Pulmonary vascular morphogenesis was abnormal in TGF-alpha mice, with attenuated and occasionally tortuous arterial branching. The ratios of right ventricle weight to left ventricle plus septal weight were increased in TGF-alpha mice, indicating pulmonary hypertension. Electron microscopy showed gaps in the capillary endothelium and extravasation of erythrocytes into the alveolar space of TGF-alpha mice. Hemorrhage and inflammatory cells were seen in distal air spaces at 1 mo of age. In adult TGF-alpha mice, alveolar remodeling, nodules, proteinaceous deposits, and inflammatory cells were seen. Immunostaining for pro-surfactant protein C showed that type II cells were abundant in the nodules, as well as neutrophils and macrophages. Trichrome staining showed that pulmonary fibrosis was minimal, apart from areas of nodular remodeling in adult TGF-alpha mice. Transient induction of TGF-alpha during early alveologenesis permanently disrupted lung structure and function and caused chronic lung disease.

Animals↗
PubMed2004

VEGF causes pulmonary hemorrhage, hemosiderosis, and air space enlargement in neonatal mice.

To determine whether increased levels of VEGF disrupt postnatal lung formation or function, conditional transgenic mice in which VEGF 164 expression was enhanced in respiratory epithelial cells were produced. VEGF expression was induced in the lungs of VEGF transgenic pups with doxycycline from postnatal day 1 through 2 and 6 wk of age. VEGF levels were higher in bronchoalveolar lavage fluid (BALF) and lung homogenates of VEGF transgenic mice compared with endogenous VEGF levels in controls. Neonatal mortality was increased by 50% in VEGF transgenic mice. Total protein content in BALF was elevated in VEGF transgenic mice. Surfactant protein B protein expression was unaltered in VEGF transgenic mice. Although postnatal alveolar and vascular development were not disrupted by VEGF expression, VEGF transgenic mice developed pulmonary hemorrhage, alveolar remodeling, and macrophage accumulation as early as 2 wk of age. Electron microscopy demonstrated abnormal alveolar capillary endothelium in the VEGF transgenic mice. In many locations, the endothelium was discontinuous with segments of attenuated endothelial cells. Large numbers of hemosiderin-laden macrophages and varying degrees of emphysema were observed in adult VEGF transgenic mice. Overexpression of VEGF in the neonatal lung increased infant mortality and caused pulmonary hemorrhage, hemosiderosis, alveolar remodeling, and inflammation.

Aging↗
PubMed2004

Interactions between pulmonary surfactant and alveolar macrophages in the pathogenesis of lung disease.

This article reviews recent findings regarding interrelationships between the pulmonary surfactant system and alveolar macrophages in the pathogenesis of human lung diseases, including pulmonary alveolar proteinosis, pulmonary infection, inflammation and obstructive lung diseases. Various components of pulmonary surfactant interact with alveolar macrophages in the modulation of innate host defense responses of the lung. In a reciprocal manner, alveolar macrophages regulate surfactant homeostasis, influencing rates of surfactant protein and phospholipid clearance and catabolism. Increasing evidence suggests that the complex interactions between the surfactant system and the alveolar macrophage are intrinsically linked to development of various lung diseases.

Animals↗
PubMed2001

Induction and apoptotic regression of lung adenocarcinomas by regulation of a K-Ras transgene in the presence and absence of tumor suppressor genes.

To investigate the role of an activated K-Ras gene in the initiation and maintenance of lung adenocarcinomas, we developed transgenic mice that express murine K-Ras4b(G12D) under the control of doxycycline in type II pneumocytes. Focal proliferative lesions of alveolar type II pneumocytes were observed as early as seven days after induction with doxycycline; after two months of induction, the lungs contained adenomas and adenocarcinomas, with focal invasion of the pleura at later stages. Removal of doxycycline caused a rapid fall in levels of mutant K-Ras RNA and concomitant apoptotic regression of both the early proliferative lesions and the tumors. Tumor burden was dramatically decreased by three days after withdrawal, and tumors were undetectable after one month. When similar experiments were performed with animals deficient in either the p53 gene or the Ink4A/Arf locus, tumors arose more quickly (within one month of exposure to doxycycline) and displayed more obvious histological features of malignancy; nevertheless, these tumors also regressed rapidly when the inducer was removed, implying that continued production of mutant K-Ras is necessary to maintain the viability of tumor cells in the absence as well as the presence of tumor suppressor genes. We also show that the appearance and regression of these pulmonary tumors can be readily monitored in anesthetized transgenic animals by magnetic resonance imaging.

Adenocarcinoma↗
PubMed2001

Surfactant protein D enhances clearance of influenza A virus from the lung in vivo.

Mice lacking surfactant protein surfactant protein D (SP-D(-/-)) and wild-type mice (SP-D(+/+)) were infected with influenza A virus (IAV) by intranasal instillation. IAV infection increased the endogenous SP-D concentration in wild-type mice. SP-D-deficient mice showed decreased viral clearance of the Phil/82 strain of IAV and increased production of inflammatory cytokines in response to viral challenge. However, the less glycosylated strain of IAV, Mem/71, which is relatively resistant to SP-D in vitro, was cleared efficiently from the lungs of SP-D(-/-) mice. Viral clearance of the Phil/82 strain of IAV and the cytokine response were both normalized by the coadministration of recombinant SP-D. Since the airway is the usual portal of entry for influenza A virus and other respiratory pathogens, SP-D is likely to play an important role in innate defense responses to IAV.

Animals↗
PubMed2001

Aquaporin 5-deficient mouse lungs are hyperresponsive to cholinergic stimulation.

Although aquaporin 5 (AQP5) is the major water channel expressed in alveolar type I cells in the lung, its actual role in the lung is a matter of considerable speculation. By using immunohistochemical staining, we show that AQP5 expression in mouse lung is not restricted to type I cells, but is also detected in alveolar type II cells, and in tracheal and bronchial epithelium. Aqp5 knockout (Aqp5(-/-)) mice were used to analyze AQP5 function in pulmonary physiology. Compared with Aqp5(+/+) mice, Aqp5(-/-) mice show a significantly increased concentration-dependent bronchoconstriction to intravenously administered Ach, as shown by an increase in total lung resistance and a decrease in dynamic lung compliance (P < 0.05). Likewise, Penh, a measure of bronchoconstriction, was significantly enhanced in Aqp5(-/-) mice challenged with aerosolized methacholine (P < 0.05). The hyperreactivity to bronchoconstriction observed in the Aqp5(-/-) mice was not due to differences in tracheal smooth muscle contractility in isolated preparations or to altered levels of surfactant protein B. These data suggest a novel pathway by which AQP5 influences bronchoconstriction. This observation is of special interest because studies to identify genetic loci involved in airway hyperresponsiveness associated with asthma bracket genetic intervals on human chromosome 12q and mouse chromosome 15, which contain the Aqp5 gene.

Acetylcholine↗
PubMed2001

The collagen-like region of surfactant protein A (SP-A) is required for correction of surfactant structural and functional defects in the SP-A null mouse.

Pulmonary surfactant isolated from gene-targeted surfactant protein A null mice (SP-A(-/-)) is deficient in the surfactant aggregate tubular myelin and has surface tension-lowering activity that is easily inhibited by serum proteins in vitro. To further elucidate the role of SP-A and its collagen-like region in surfactant function, we used the human SP-C promoter to drive expression of rat SP-A (rSPA) or SP-A containing a deletion of the collagen-like domain (DeltaG8-P80) in the Clara cells and alveolar type II cells of SP-A(-/-) mice. The level of the SP-A in the alveolar wash of the SP-A(-/-,rSP-A) and SP-A(-/-,DeltaG8-P80) mice was 6.1-and 1.3-fold higher, respectively, than in the wild type controls. Tissue levels of saturated phosphatidylcholine were slightly reduced in the SP-A(-/-,rSP-A) mice compared with SP-A(-/-) littermates. Tubular myelin was present in the large surfactant aggregates isolated from the SP-A(-/-,rSP-A) lines but not in the SP-A(-/-,DeltaG8-P80) mice or SP-A(-/-) controls. The equilibrium and minimum surface tensions of surfactant from the SP-A(-/-,rSP-A) mice were similar to SP-A(-/-) controls, but both were markedly elevated in the SP-A(-/-,DeltaG8-P80) mice. There was no defect in the surface tension-lowering activity of surfactant from SP-A(+/+,DeltaG8-P80) mice, indicating that the inhibitory effect of DeltaG8-P80 on surface activity can be overcome by wild type levels of mouse SP-A. The surface activity of surfactant isolated from the SP-A(-/-,rSP-A) but not the SP-A(-/-,DeltaG8-P80) mice was more resistant than SP-A(-/-) littermate control animals to inhibition by serum proteins in vitro. Pressure volume relationships of lungs from the SP-A(-/-), SP-A(-/-,rSP-A), and SP-A(-/-,DeltaG8-P80) lines were very similar. These data indicate that expression of SP-A in the pulmonary epithelium of SP-A(-/-) animals restores tubular myelin formation and resistance of isolated surfactant to protein inhibition by a mechanism that is dependent on the collagen-like region.

Animals↗
PubMed2001

Defects in pulmonary vasculature and perinatal lung hemorrhage in mice heterozygous null for the Forkhead Box f1 transcription factor.

Decreased pulmonary expression of Forkhead Box f1 (Foxf1) transcription factor was associated with lethal alveolar hemorrhage in 55% of the Foxf1 +/- newborn mice. The severity of the pulmonary abnormalities correlates with the levels of Foxf1 mRNA. Defects in alveolarization and vasculogenesis were observed in subsets of the Foxf1 +/- mice with relatively low levels of expression from the normal Foxf1 allele. Lung hemorrhage was coincident with disruption of the mesenchymal-epithelial cell interfaces in the alveolar and bronchiolar regions of the lung parenchyma and was associated with increased apoptosis and reduced surfactant protein B (SP-B) expression. Finally, the lung defect associated with the Foxf1 +/- mutation was accompanied by reduced expression of vascular endothelial growth factor (VEGF), the VEGF receptor 2 (Flk-1), bone morphogenetic protein 4 (Bmp-4), and the transcription factors of the Brachyury T-Box family (Tbx2-Tbx5) and Lung Kruppel-like Factor. Reduction in the level of Foxf1 caused neonatal pulmonary hemorrhage and abnormalities in alveologenesis, implicating this transcription factor in the regulation of mesenchyme-epithelial interaction critical for lung morphogenesis.

Alleles↗
PubMed2001

Surfactant protein D regulates NF-kappa B and matrix metalloproteinase production in alveolar macrophages via oxidant-sensitive pathways.

Targeted ablation of the surfactant protein D (SP-D) gene caused progressive pulmonary emphysema associated with pulmonary infiltration by foamy alveolar macrophages (AMs), increased hydrogen peroxide production, and matrix metalloproteinase (MMP)-2, -9, and -12 expression. In the present study, the mechanisms by which SP-D influences macrophage MMP activity were assessed in AMs from SP-D(-/-) mice. Tissue lipid peroxides and reactive carbonyls were increased in lungs of SP-D(-/-) mice, indicating oxidative stress. Immunohistochemical staining of AMs from SP-D(-/-) mice demonstrated that NF-kappaB was highly expressed and translocated to the nucleus. Increased NF-kappaB binding was detected by EMSA in nuclear extracts of AMs isolated from SP-D(-/-) mice. Antioxidants N-acetylcysteine and pyrrolidine dithiocarbamate inhibited MMP production by AMs from SP-D(-/-) mice. To assess whether increased oxidant production influenced NF-kappaB activation and production of MMP-2 and -9, AMs from SP-D(-/-) mice were treated with the NADPH oxidase inhibitors diphenylene iodonium chloride and apocynin. Inhibition of NADPH oxidase suppressed NF-kappaB binding by nuclear extracts and decreased production of MMP-2 and 9 in AMs from SP-D(-/-) mice. SN-50, a synthetic NF-kappaB-inhibitory peptide, decreased MMP production by AMs from SP-D(-/-) mice. Oxidant production and reactive oxygen species were increased in lungs of SP-D(-/-) mice, in turn activating NF-kappaB and MMP expression. SP-D plays an unexpected inhibitory role in the regulation of NF-kappaB in AMs.

Acetylcysteine↗
PubMed2001

Altered stability of pulmonary surfactant in SP-C-deficient mice.

The surfactant protein C (SP-C) gene encodes an extremely hydrophobic, 4-kDa peptide produced by alveolar epithelial cells in the lung. To discern the role of SP-C in lung function, SP-C-deficient (-/-) mice were produced. The SP-C (-/-) mice were viable at birth and grew normally to adulthood without apparent pulmonary abnormalities. SP-C mRNA was not detected in the lungs of SP-C (-/-) mice, nor was mature SP-C protein detected by Western blot of alveolar lavage from SP-C (-/-) mice. The levels of the other surfactant proteins (A, B, D) in alveolar lavage were comparable to those in wild-type mice. Surfactant pool sizes, surfactant synthesis, and lung morphology were similar in SP-C (-/-) and SP-C (+/+) mice. Lamellar bodies were present in SP-C (-/-) type II cells, and tubular myelin was present in the alveolar lumen. Lung mechanics studies demonstrated abnormalities in lung hysteresivity (a term used to reflect the mechanical coupling between energy dissipative forces and tissue-elastic properties) at low, positive-end, expiratory pressures. The stability of captive bubbles with surfactant from the SP-C (-/-) mice was decreased significantly, indicating that SP-C plays a role in the stabilization of surfactant at low lung volumes, a condition that may accompany respiratory distress syndrome in infants and adults.

Animals↗
PubMed2001

Overexpression of manganese superoxide dismutase (MnSOD) in whole lung or alveolar type II cells of MnSOD transgenic mice does not provide intrinsic lung irradiation protection.

Intratracheal (IT) injection of the transgene for human manganese superoxide dismutase in plasmid/liposome (SOD2-PL) complex prior to irradiation protects C57BL/6J mice from whole lung irradiation-induced organizing alveolitis/fibrosis. Transgene mRNA was detected in alveolar type II (AT-II) and tracheobronchial tree cells explanted to culture 48 hours after gene therapy. To determine whether constitutive overexpression of murine MnSOD (Sod2) in whole lung or surfactant promoter-restricted AT-II cells (SP1)-SOD2 mice would provide intrinsic radioresistance, transgenic mice of two strains were compared with age-matched controls. Other groups of surfactant promoter-restricted (SP1)-SOD2 transgenic mice or control FeVB/NHsd mice received IT SOD2-PL gene therapy prior to irradiation. There was no significant intrinsic lung protection in either strain of MnSOD transgenic mice. The SP1-SOD2 transgenic mice were protected from lung damage by IT injection of the human SOD2-PL complex 24 hours prior to irradiation. Thus, overexpression of either human SOD2 or murine Sod2 in the lungs of transgenic mice does not provide intrinsic lung irradiation protection. The overexpression of SOD2 in the SP1-SOD2 mice may have made the mice more sensitive to irradiation.

Animals↗
PubMed2001

Immunosuppressed surfactant protein A-deficient mice have increased susceptibility to Pneumocystis carinii infection.

Immunosuppressed Swiss Black mice deficient in surfactant protein A (SP-A(-/-)) and wild-type control mice (SP-A(+/+)) were exposed to Pneumocystis carinii by environmental exposure, intratracheal inoculation, and direct exposure to other infected animals. The frequency and intensity of P. carinii infection were significantly greater in the SP-A(-/-) mice by all 3 methods of exposure. P. carinii free of SP-A and alveolar macrophages were isolated from SP-A(-/-) mice and were tested in an in vitro attachment assay. Pretreatment of P. carinii with human SP-A resulted in a significant dose-dependent increase of the adherence of P. carinii to the macrophages. Thus, SP-A plays a role in host defense against P. carinii in vivo, perhaps by functioning as a nonimmune opsonin.

Animals↗
PubMed2001

Activity of pulmonary surfactant protein-D (SP-D) in vivo is dependent on oligomeric structure.

Pulmonary surfactant protein-D (SP-D) is a member of the collectin family of C-type lectins that is synthesized in many tissues including respiratory epithelial cells in the lung. SP-D is assembled predominantly as dodecamers consisting of four homotrimeric subunits each. Association of these subunits is stabilized by interchain disulfide bonds involving two conserved amino-terminal cysteine residues (Cys-15 and Cys-20). Mutant recombinant rat SP-D lacking these residues (RrSP-Dser15/20) is secreted in cell culture as trimeric subunits rather than as dodecamers. In this study, transgenic mice that express this mutant were generated to elucidate the functional importance of SP-D oligomerization in vivo. Expression of RrSP-Dser15/20 failed to correct the pulmonary phospholipid accumulation and emphysema characteristic of SP-D null (mSP-D-/-) mice. Expression of high concentrations of the mutant protein in wild-type mice reduced the abundance of disulfide cross-linked oligomers of endogenous SP-D in the bronchoalveolar lavage fluid and demonstrated a phenotype that partially overlapped with that of the SP-D-/- mice; the animals developed emphysema and foamy macrophages without the associated abnormalities in alveolar phospholipids typical of SP-D-/- mice. Development of foamy macrophages in SP-D-deficient mice is not secondary to the increased abundance of surfactant phospholipids. Disulfide cross-linked SP-D oligomers are required for the regulation of surfactant phospholipid homeostasis and the prevention of emphysema and foamy macrophages in vivo.

Animals↗
PubMed2001

TGF-beta1 perturbs vascular development and inhibits epithelial differentiation in fetal lung in vivo.

Members of the transforming growth factor beta (TGF-beta) family of polypeptides have been implicated in morphogenesis and differentiation in numerous tissues, including the lung. In order to further define effects of TGF-beta signaling in lung morphogenesis, a constitutively active form of TGF-beta1 was expressed in respiratory epithelial cells of the fetal mouse lung in vivo. Expression of TGF-beta1 arrested lung morphogenesis in the pseudoglandular stage of development, inhibiting synthesis of differentiation-dependent proteins, SP-B, SP-C, and CCSP, and maintaining embryonic patterns of staining for thyroid transcription factor-1 (TTF-1) and hepatocyte nuclear factor-3beta (HNF-3beta). The pulmonary mesenchyme was thickened and vascular density was increased by TGF-beta1. TGF-beta1 decreased expression of vascular endothelial growth factor-A (VEGF-A) mRNA and protein, and the abundance of Flk-1 mRNA in the lung mesenchyme. Distribution of platelet-endothelial cell adhesion molecule (PECAM)-1, a marker of pulmonary blood vessels, was altered, and ultrastructural studies demonstrated that TGF-beta1 inhibited vascular development in the fetal lung. TGF-beta1 perturbed both epithelial cell differentiation and formation of the pulmonary vasculature, supporting the concept that precise control of signaling via the TGF-beta receptor pathway is critical for normal lung morphogenesis.

Animals↗
PubMed2001

Fetal monkey surfactants after intra-amniotic or maternal administration of betamethasone and thyroid hormone.

OBJECTIVE: To compare direct intra-amniotic injection of betamethasone and thyroxine (T4) with maternal treatment and controls for accelerating pulmonary surfactant production. METHODS: Twelve pregnant monkeys (Macaca mulatta) on gestational day 125 (term 165 +/- 10 days) had surfactant protein A and B concentrations measured in amniotic fluid. In four controls, normal saline was injected into the amniotic fluid; four others (intra-amniotic) received intra-amniotic betamethasone (1 mg) and T4 (60 microg); and in four others (maternal), the dam was given betamethasone (12 mg) intramuscularly, repeated in 24 hours, plus TRH (400 microg) intravenously, repeated every 6 hours for 24 hours. Seventy-two hours after the initial amniocentesis, a hysterotomy was performed and fetal tissue and amniotic fluid harvested for determination of surfactant protein A and B concentrations and immunohistochemical staining for surfactant protein A. RESULTS: Amniotic fluid surfactant protein A was higher with intra-amniotic injection than with maternal treatment (P <.04) or controls (P =.07). Amniotic fluid surfactant protein B was higher in the intra-amniotic group than in controls (P =.06). Immunohistochemical staining for surfactant protein A in the lung tissue was increased in the intra-amniotic group compared with controls (0.145 +/- 0.01 versus 0.097 +/- 0.001, percent positive staining for surfactant protein A cells per lung tissue cells; P <.03). Birth weight was greater in the intra-amniotic group compared with the maternal group (P <.03) although not different from the controls. Finally, gut motility and the presence of formed meconium were increased in the intra-amniotic group compared with the other groups (P <.05). CONCLUSION: Intra-amniotic injection of betamethasone and T4 enhanced lung (and possibly intestinal) maturation of the preterm rhesus fetal monkey compared with maternal injections.

Amniotic Fluid↗