The Novel Small Molecule BTB Inhibits Pro-Fibrotic Fibroblast Behavior though Inhibition of RhoA Activity

Idiopathic pulmonary fibrosis (IPF) is a progressive, chronic, interstitial lung disease with a poor prognosis. Although specific anti-fibrotic medications are now available, the median survival time following diagnosis remains very low, and new therapies are urgently needed. To uncover novel therapeutic targets, we examined how biochemical properties of the fibrotic lung are different from the healthy lung. Previous work identified lactate as a metabolite that is upregulated in IPF lung tissue. Importantly, inhibition of the enzyme responsible for lactate production prevents fibrosis in vivo. Further studies revealed that fibrotic lesions of the lung experience a significant decline in tissue pH, likely due to the overproduction of lactate. It is not entirely clear how cells in the lung respond to changes in extracellular pH, but a family of proton sensing G-protein coupled receptors has been shown to be activated by reductions in extracellular pH. This work examines the expression profiles of proton sensing GPCRs in non-fibrotic and IPF-derived primary human lung fibroblasts. We identify TDAG8 as a proton sensing GPCR that is upregulated in IPF fibroblasts and that knockdown of TDAG8 dampens myofibroblast differentiation. To our surprise, BTB, a proposed positive allosteric modulator of TDAG8, inhibits myofibroblast differentiation. Our data suggest that BTB does not require TDAG8 to inhibit myofibroblast differentiation, but rather inhibits myofibroblast differentiation through suppression of RhoA mediated signaling. Our work highlights the therapeutic potential of BTB as an anti-fibrotic treatment and expands upon the importance of RhoA-mediated signaling pathways in the context of myofibroblast differentiation. Furthermore, this works also suggests that TDAG8 inhibition may have therapeutic relevance in the treatment of IPF.

Cell-Type-Specific Effects of the Ovarian Cancer G-Protein Coupled Receptor (OGR1) on Inflammation and Fibrosis; Potential Implications for Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a disease characterized by irreversible lung scarring. The pathophysiology is not fully understood, but the working hypothesis postulates that a combination of epithelial injury and myofibroblast differentiation drives progressive pulmonary fibrosis. We previously demonstrated that a reduction in extracellular pH activates latent TGF-β1, and that TGF-β1 then drives its own activation, creating a feed-forward mechanism that propagates myofibroblast differentiation. Given the important roles of extracellular pH in the progression of pulmonary fibrosis, we sought to identify whether pH mediates other cellular phenotypes independent of TGF-β1. Proton-sensing G-protein coupled receptors are activated by acidic environments, but their role in fibrosis has not been studied. Here, we report that the Ovarian Cancer G-Protein Coupled Receptor1 (OGR1 or GPR68) has dual roles in both promoting and mitigating pulmonary fibrosis. We demonstrate that OGR1 protein expression is significantly reduced in lung tissue from patients with IPF and that TGF-β1 decreases OGR1 expression. In fibroblasts, OGR1 inhibits myofibroblast differentiation and does not contribute to inflammation. However, in epithelial cells, OGR1 promotes epithelial to mesenchymal transition (EMT) and inflammation. We then demonstrate that sub-cellular localization and alternative signaling pathways may be responsible for the differential effect of OGR1 in each cell type. Our results suggest that strategies to selectively target OGR1 expression may represent a novel therapeutic strategy for pulmonary fibrosis.

Ogerin mediated inhibition of TGF-β(1) induced myofibroblast differentiation is potentiated by acidic pH

Transforming growth factor beta (TGF-β) induced myofibroblast differentiation is central to the pathological scarring observed in Idiopathic Pulmonary Fibrosis (IPF) and other fibrotic diseases. Our lab has recently identified expression of GPR68 (Ovarian Cancer Gene Receptor 1, OGR1), a pH sensing G-protein coupled receptor, as a negative regulator of TGF-β induced profibrotic effects in primary human lung fibroblasts (PHLFs). We therefore hypothesized that small molecule activators of GPR68 would inhibit myofibroblast differentiation. Ogerin is a positive allosteric modulator (PAM) of GPR68, inducing a leftward shift of the dose response curve to proton induced signaling. Using PHLFs derived from patients with both non-fibrotic and IPF diagnoses, we show that Ogerin inhibits, and partially reverses TGF-β induced myofibroblast differentiation in a dose dependent manner. This occurs at the transcriptional level without inhibition of canonical TGF-β induced SMAD signaling. Ogerin induces PKA dependent CREB phosphorylation, a marker of Gαs pathway activation. The ability of Ogerin to inhibit both basal and TGF-β induced collagen gene transcription, and induction of Gαs signaling is enhanced at an acidic pH (pH 6.8). Similar findings were also found using fibroblasts derived from dermal, intestinal, and orbital tissue. The biological role of GPR68 in different tissues, cell types, and disease states is an evolving and emerging field. This work adds to the understanding of Gαs coupled GPCRs in fibrotic lung disease, the ability to harness the pH sensing properties of GPR68, and conserved mechanisms of fibrosis across different organ systems.

The effect of air pollution on the transcriptomics of the immune response to respiratory infection

Combustion related particulate matter air pollution (PM) is associated with an increased risk of respiratory infections in adults. The exact mechanism underlying this association has not been determined. We hypothesized that increased concentrations of combustion related PM would result in dysregulation of the innate immune system. This epidemiological study includes 111 adult patients hospitalized with respiratory infections who underwent transcriptional analysis of their peripheral blood. We examined the association between gene expression at the time of hospitalization and ambient measurements of particulate air pollutants in the 28 days prior to hospitalization. For each pollutant and time lag, gene-specific linear models adjusting for infection type were fit using LIMMA (Linear Models For Microarray Data), and pathway/gene set analyses were performed using the CAMERA (Correlation Adjusted Mean Rank) program. Comparing patients with viral and/or bacterial infection, the expression patterns associated with air pollution exposure differed. Adjusting for the type of infection, increased concentrations of Delta-C (a marker of biomass smoke) and other PM were associated with upregulation of iron homeostasis and protein folding. Increased concentrations of black carbon (BC) were associated with upregulation of viral related gene pathways and downregulation of pathways related to antigen presentation. The pollutant/pathway associations differed by lag time and by type of infection. This study suggests that the effect of air pollution on the pathogenesis of respiratory infection may be pollutant, timing, and infection specific.

The self-fulfilling prophecy of pulmonary fibrosis: a selective inspection of pathological signalling loops

Pulmonary fibrosis is a devastating, progressive disease and carries a prognosis worse than most cancers. Despite ongoing research, the mechanisms that underlie disease pathogenesis remain only partially understood. However, the self-perpetuating nature of pulmonary fibrosis has led several researchers to propose the existence of pathological signalling loops. According to this hypothesis, the normal wound-healing process becomes corrupted and results in the progressive accumulation of scar tissue in the lung. In addition, several negative regulators of pulmonary fibrosis are downregulated and, therefore, are no longer capable of inhibiting these feed-forward loops. The combination of pathological signalling loops and loss of a checks and balances system ultimately culminates in a process of unregulated scar formation. This review details specific signalling pathways demonstrated to play a role in the pathogenesis of pulmonary fibrosis. The evidence of detrimental signalling loops is elucidated with regard to epithelial cell injury, cellular senescence and the activation of developmental and ageing pathways. We demonstrate where these loops intersect each other, as well as common mediators that may drive these responses and how the loss of pro-resolving mediators may contribute to the propagation of disease. By focusing on the overlapping signalling mediators among the many pro-fibrotic pathways, it is our hope that the pulmonary fibrosis community will be better equipped to design future trials that incorporate the redundant nature of these pathways as we move towards finding a cure for this unrelenting disease.

Interpretation of Valence Band X-Ray Spectra

X -ray spectra arising from the valence bands of solids are useful for basic studies of the electronic structure of most materials and for practical measurements of unknowns to obtain information on local atomic structure and material properties as well as chemical composition. Understanding the characteristics of valence band spectra is prerequisite to their fullest use. One-electron and many-body aspects of the x-ray emission process, and the effects of experimental conditions, must be understood and are reviewed. Interpretation of spectral features and determination of electronic structure are complementary parts of one procedure which is based on the use of bonding theory. The various band and bond theories which are finding use for spectral interpretation are briefly reviewed. Calculation of the electronic structure of aluminum metal and quartz, and interpretation of their x-ray spectra, are examples which illustrate basic work with valence band spectra.

Role of cAMP-phosphodiesterase 1C signaling in regulating growth factor receptor stability, vascular smooth muscle cell growth, migration, and neointimal hyperplasia

RATIONALE

Neointimal hyperplasia characterized by abnormal accumulation of vascular smooth muscle cells (SMCs) is a hallmark of occlusive disorders such as atherosclerosis, postangioplasty restenosis, vein graft stenosis, and allograft vasculopathy. Cyclic nucleotides are vital in SMC proliferation and migration, which are regulated by cyclic nucleotide phosphodiesterases (PDEs).

OBJECTIVE

Our goal is to understand the regulation and function of PDEs in SMC pathogenesis of vascular diseases.

METHODS AND RESULTS

We performed screening for genes differentially expressed in normal contractile versus proliferating synthetic SMCs. We observed that PDE1C expression was low in contractile SMCs but drastically elevated in synthetic SMCs in vitro and in various mouse vascular injury models in vivo. In addition, PDE1C was highly induced in neointimal SMCs of human coronary arteries. More importantly, injury-induced neointimal formation was significantly attenuated by PDE1C deficiency or PDE1 inhibition in vivo. PDE1 inhibition suppressed vascular remodeling of human saphenous vein explants ex vivo. In cultured SMCs, PDE1C deficiency or PDE1 inhibition attenuated SMC proliferation and migration. Mechanistic studies revealed that PDE1C plays a critical role in regulating the stability of growth factor receptors, such as PDGF receptor β (PDGFRβ) known to be important in pathological vascular remodeling. PDE1C interacts with low-density lipoprotein receptor-related protein-1 and PDGFRβ, thus regulating PDGFRβ endocytosis and lysosome-dependent degradation in an low-density lipoprotein receptor-related protein-1-dependent manner. A transmembrane adenylyl cyclase cAMP-dependent protein kinase cascade modulated by PDE1C is critical in regulating PDGFRβ degradation.

CONCLUSIONS

These findings demonstrated that PDE1C is an important regulator of SMC proliferation, migration, and neointimal hyperplasia, in part through modulating endosome/lysosome-dependent PDGFRβ protein degradation via low-density lipoprotein receptor-related protein-1.

Abstract 165: cAMP-Phosphodiesterase 1C Regulates Neointimal Hyperplasia by Controlling Platelet-Derived Growth Factor Receptor ß Degradation via the Endosome-Lysosome Pathway

Neointimal hyperplasia is associated with the development of diverse vascular diseases such as atherosclerosis, vein bypass graft disease and restenosis after percutaneous coronary interventions. Vascular injury-mediated neointimal hyperplasia involves the phenotypic modulation, migration and proliferation of vascular smooth muscle cells (VSMCs). Cyclic nucleotide is vital in regulating VSMC migration and proliferation, which are controlled by cyclic nucleotide phosphodiesterase (PDE) isozymes. To identify the regulation and function of PDEs in VSMC pathogenesis of vascular diseases, we performed systematic screening for all 22 known PDE genes in normal contractile VSMCs and proliferating synthetic VSMCs. Interestingly, we observed that expression of PDE1C was very low in normal contractile VSMCs but drastically elevated in synthetic VSMCs in vitro as well as in vivo in various mouse models of vascular injuries, including carotid artery ligation, femoral artery wire injury and vein bypass graft. Consistently, PDE1C is also highly induced in VSMCs in neointimal lesion of human coronary artery. More importantly, injury-induced neointimal formation was significantly attenuated in pde1c-deficient mice or by perivascular administration of PDE1 inhibitor. Furthermore, PDE1 inhibition also reduced the spontaneous vascular remodeling of human saphenous vein explant in an ex vivo culture model. Mechanistic studies revealed that PDE1C plays a critical role in regulating the stability of PDGF receptor beta (PDGFR-β). We found that PDE1C knockdown or inhibition markedly decreased the levels of PDGFR-β protein but not mRNA, which was blocked by endosome and lysosome inhibitors. Furthermore, PDE1C inhibition is capable of promoting PDGFR-β internalization and attenuating PDGFR-β membrane accumulation. Finally, we found that PDE1C co-localized with PDGFR-β on cell membrane, which was able to regulate PDGFR-β protein degradation through modulating a transmembrane adenylyl cyclase-cAMP-PKA signaling. Taken together, our present data demonstrated that PDE1C plays a critical role in regulating VSMC proliferation and neointimal hyperplasia, in part, through promoting endosome/lysosome dependent PDGFR-β protein degradation.

Cyclic nucleotide phosphodiesterase 1 regulates lysosome-dependent type I collagen protein degradation in vascular smooth muscle cells

OBJECTIVE

The phenotypic modulation of vascular smooth muscle cells (VSMCs) to a synthetic phenotype is vital during pathological vascular remodeling and the development of various vascular diseases. An increase in type I collagen (collagen I) has been implicated in synthetic VSMCs, and cyclic nucleotide signaling is critical in collagen I regulation. Herein, we investigate the role and underlying mechanism of cyclic nucleotide phosphodiesterase 1 (PDE1) in regulating collagen I in synthetic VSMCs.

METHODS AND RESULTS

The PDE1 inhibitor IC86340 significantly reduced collagen I in human saphenous vein explants undergoing spontaneous remodeling via ex vivo culture. In synthetic VSMCs, high basal levels of intracellular and extracellular collagen I protein were markedly decreased by IC86340. This attenuation was due to diminished protein but not mRNA. Inhibition of lysosome function abolished the effect of IC86340 on collagen I protein expression. PDE1C but not PDE1A is the major isoform responsible for mediating the effects of IC86340. Bicarbonate-sensitive soluble adenylyl cyclase/cAMP signaling was modulated by PDE1C, which is critical in collagen I degradation in VSMCs.

CONCLUSIONS

These data demonstrate that PDE1C regulates soluble adenylyl cyclase/cAMP signaling and lysosome-mediated collagen I protein degradation, and they suggest that PDE1C plays a critical role in regulating collagen homeostasis during pathological vascular remodeling.

A model of ischemia and reperfusion increases JNK activity, inhibits the association of BAD and 14-3-3, and induces apoptosis of rabbit spinal neurocytes

It is now well established that the protein BAD (a pro-apoptotic Bcl-2 family protein) plays a pivotal role in determining cell death and survival. The c-Jun N-terminal kinase (JNK) pathway has been hypothesized to be involved in regulation of BAD. To clarify the role of BAD within the JNK pathway, a randomized, controlled study was designed using a rabbit model of ischemic spinal cord injury [5,8]. Forty-five white adult New England rabbits were randomly assigned to one of the three groups: sham-operation group (n=5), vehicle group (n=20), and JNK inhibitor group (n=20). We examined alterations in spinal tissue morphology, local concentration and cellular locations of key regulatory proteins, and protein-protein interactions. Changes in spinal cord morphology were observed with hematoxylin and eosin (H&E) staining and electron microscopy. In the vehicle group, the amount of JNK phosphorylation, cytochrome c release, and the interaction between BAD and Bcl-XL or Bcl-2 were increased compared with the JNK inhibitor group. Similarly, the phosphorylation of BAD (Ser136) and the interaction between BAD and 14-3-3 were decreased in the vehicle group. Immunohistochemical studies showed that cytoplasmic location of 14-3-3 and p-BAD (Ser136) were decreased in the vehicle group compared with the JNK inhibitor group. In addition, mitochondrial morphology was better preserved and the percentage of apoptosis was lower when JNK was inhibited. These results indicate that the JNK pathway has a critical role in the survival of neurocytes by regulating the interaction between BAD and 14-3-3.

Role of Ca2+/calmodulin-stimulated cyclic nucleotide phosphodiesterase 1 in mediating cardiomyocyte hypertrophy

RATIONALE

Cyclic nucleotide phosphodiesterases (PDEs) through the degradation of cGMP play critical roles in maintaining cardiomyocyte homeostasis. Ca(2+)/calmodulin (CaM)-activated cGMP-hydrolyzing PDE1 family may play a pivotal role in balancing intracellular Ca(2+)/CaM and cGMP signaling; however, its function in cardiomyocytes is unknown.

OBJECTIVE

Herein, we investigate the role of Ca(2+)/CaM-stimulated PDE1 in regulating pathological cardiomyocyte hypertrophy in neonatal and adult rat ventricular myocytes and in the heart in vivo.

METHODS AND RESULTS

Inhibition of PDE1 activity using a PDE1-selective inhibitor, IC86340, or downregulation of PDE1A using siRNA prevented phenylephrine induced pathological myocyte hypertrophy and hypertrophic marker expression in neonatal and adult rat ventricular myocytes. Importantly, administration of the PDE1 inhibitor IC86340 attenuated cardiac hypertrophy induced by chronic isoproterenol infusion in vivo. Both PDE1A and PDE1C mRNA and protein were detected in human hearts; however, PDE1A expression was conserved in rodent hearts. Moreover, PDE1A expression was significantly upregulated in vivo in the heart and myocytes from various pathological hypertrophy animal models and in vitro in isolated neonatal and adult rat ventricular myocytes treated with neurohumoral stimuli such as angiotensin II (Ang II) and isoproterenol. Furthermore, PDE1A plays a critical role in phenylephrine-induced reduction of intracellular cGMP- and cGMP-dependent protein kinase (PKG) activity and thereby cardiomyocyte hypertrophy in vitro.

CONCLUSIONS

These results elucidate a novel role for Ca(2+)/CaM-stimulated PDE1, particularly PDE1A, in regulating pathological cardiomyocyte hypertrophy via a cGMP/PKG-dependent mechanism, thereby demonstrating Ca(2+) and cGMP signaling cross-talk during cardiac hypertrophy.

Activation of ASK1 during reperfusion of ischemic spinal cord

Apoptosis signal-regulating kinase 1 (ASK1) is a mitogen-activated protein kinase kinase kinase (MAPKKK), which plays a pivotal role in cell apoptosis. To determine the mechanism of ASK1 induction during reperfusion of ischemic spinal tissue, we used a model of rabbit spinal cord ischemia and reperfusion. To assess the role of ASK1 in spinal cord ischemia-reperfusion injuries, we examined alterations in spinal tissue morphology, protein-protein interactions, and activation of key members of the ASK1-mediated signaling pathway. Changes in spinal cord morphology were observed with hematoxylin and eosin (H&E) staining and electron microscopy. The phosphorylation levels of ASK1, JNK, and p38 were assessed by immunoblotting proteins from animals that received 30 min of ischemia followed by 1 or 24h of reperfusion. We observed increased phosphorylation of ASK1, JNK, and p38 after reperfusing ischemic spinal cords. Immunohistochemical studies were performed to determine the cellular localization of phosphorylated ASK1 (pASK1) and 14-3-3. Following reperfusion for 24h, we observed increased cytoplasmic localization of pASK1 and decreased cytoplasmic localization of 14-3-3. Immunoprecipitation analyses suggested that 14-3-3 dissociates from ASK1 during reperfusion of ischemic spinal cords. These results indicate that activation of ASK1 may play an important role in the apoptotic signaling mechanisms that occur in reperfused spinal cord injuries.

Role of nuclear Ca2+/calmodulin-stimulated phosphodiesterase 1A in vascular smooth muscle cell growth and survival

In response to biological and mechanical injury, or in vitro culturing, vascular smooth muscle cells (VSMCs) undergo phenotypic modulation from a differentiated "contractile" phenotype to a dedifferentiated "synthetic" one. This results in the capacity to proliferate, migrate, and produce extracellular matrix proteins, thus contributing to neointimal formation. Cyclic nucleotide phosphodiesterases (PDEs), by hydrolyzing cAMP or cGMP, are critical in the homeostasis of cyclic nucleotides that regulate VSMC growth. Here, we demonstrate that PDE1A, a Ca2+-calmodulin-stimulated PDE preferentially hydrolyzing cGMP, is predominantly cytoplasmic in medial "contractile" VSMCs but is nuclear in neointimal "synthetic" VSMCs. Using primary VSMCs, we show that cytoplasmic and nuclear PDE1A were associated with a contractile marker (SM-calponin) and a growth marker (Ki-67), respectively. This suggests that cytoplasmic PDE1A is associated with the "contractile" phenotype, whereas nuclear PDE1A is with the "synthetic" phenotype. To determine the role of nuclear PDE1A, we examined the effects loss-of-PDE1A function on subcultured VSMC growth and survival using PDE1A RNA interference and pharmacological inhibition. Reducing PDE1A function significantly attenuated VSMC growth by decreasing proliferation via G1 arrest and inducing apoptosis. Inhibiting PDE1A also led to intracellular cGMP elevation, p27Kip1 upregulation, cyclin D1 downregulation, and p53 activation. We further demonstrated that in subcultured VSMCs redifferentiated by growth on collagen gels, cytoplasmic PDE1A regulates myosin light chain phosphorylation with little effect on apoptosis, whereas inhibiting nuclear PDE1A has the opposite effects. These suggest that nuclear PDE1A is important in VSMC growth and survival and may contribute to the neointima formation in atherosclerosis and restenosis.

Plasma production from ultraviolet-transmitting targets using subpicosecond ultraviolet radiation

Plasma produced from ultraviolet-transmitting solid targets undergoing intense (>10(16) W/cm(2)) subpicosecond (~600 fs) ultraviolet (248 nm) irradiation have been studied under conditions for which no interfering prepulse plasma is generated. Time and spatially integrated measurements of the x-ray emission for H-like and He-like Mg and Si were found to be consistent with LASNEX calculations that model the laser-target interaction.

Effects of an ACTH 4-9 analog on auditory evoked brainstem responses and middle latency responses

Early and middle latency auditory evoked potentials (EAEPs and MAEPs) were recorded from thirteen male volunteers after oral administration of either 40 mg of an ACTH 4-9 analog (ORG 2766) or placebo. Main results indicate slightly longer latencies of the later components of the EAEPs after ACTH 4-9 analog. Effects of differences in treatment were clearest with very high stimulus rates. Therefore, these effects do not lend themselves for the explanation of ACTH 4-9 analog-induced changes in long latency auditory evoked potentials of cortical origin obtained with comparatively slow stimulus rates in earlier studies. In addition, the ACTH 4-9 analog inhibited a decrease in amplitudes of the Na component of the MAEP across the session. This latter result may be in line with dishabituating actions of the peptide.

X-ray applications of self-scanning silicon diode arrays

A linear diode array consisting of 512 elements was used to measure soft x rays from laser-produced plasmas. Three modes of operation were tested, with the array behind (a) low-resolution filters, (b) a high-resolution spectrograph, and (c) a collimation device. The diode array used in this work has a higher fluence threshold, less dynamic range, and poorer spatial resolution at 2 ke V than Kodak No-Screen x-ray film. However, the immediate electronic readout characteristics of diode arrays make them attractive for some applications.