R&D Systems Cytokine Bulletin spring | 2007 cytokine BULLETIN Inside page 2 MMP-12 in Smoking-Related Pulmonary Disease page 3 Regulation of VE-Cadherin & VEGF R2 by VEGF page 4 Sonic Hedgehog A morphogen involved in axon guidance BIObrief Mini-Poster Integrin Subunit Interactions page 5 RECENT CITATIONS Leptin & Leptin Receptor page 6 How to Find Figure 1. Hypothesized mechanism of Notch­mediated neural stem cell expansion in vivo, based on infusion of soluble Notch ligand in the rat model. In vitro studies in fetal neural stem cells show that Notch activation by DLL4 induces a cytoplasmic signaling Technical Information cascade that preserves fetal neural stem cell pluripotency and encourages cell expansion through STAT3­dependent Sonic hedge­ @ www.RnDSystems.com hog (Shh) release. (adapted from reference 4) MEETINGS Taking Advantage of Notch in Stem Cell Expansion page 7 The future utilization of stem cell therapy for Androutsellis­Theotokis and colleagues outlined NEW TOOLS neurodegenerative disease has been impeded by a signaling cascade initiated by Notch ligands, Recombinant Proteases the limited numbers of stem cells that can be gen­ Delta­like 4 (DLL4) and Jagged 1 (Jag1), that of the Renin-Angiotensin erated in vitro for transplantation, the potential increased fetal neural stem cell (NSC) survival System (RAS) immune response to the transplanted cells, and without inducing differentiation in vitro.4 This the sparse population of endogenous progenitor pathway includes the obligate cleavage of Nicd. page 8 cells that exist in vivo. Thus, in addition to mas­ However, the rapid timeline of cell expansion TECHNICAL NOTES tering the isolation and molecular guidance of indicates that Nicd influences cytoplasmic Assessing the Pluripotent stem cells, research is focusing on understanding effectors rather than, or in addition to, the Status of Stem Cells mechanisms that increase stem cell numbers and commonly­associated yet delayed transcriptional survival, and minimize host rejection. response. Examination of kinase activation and Notch encodes a transmembrane receptor with administration of JAK and p38 kinase inhibitors signaling integral to development and cancer. identified that DLL4 and Jag1 led to activation of Akt kinase and mammalian target of rapamycin Tools for Cell Biology Research Notch signaling occurs through ligand­induced cleavage that frees the Notch intracellular do­ (mTOR). Both are serine/threonine kinases re­ main (Nicd) to enter the nucleus and alter gene lated to cell proliferation and differentiation, with expression via tissue­specific transcription fac­ downstream phosphorylation of transcription tors.1 Among numerous roles in nervous system factor STAT3. development, Notch is imperative in stem cell Other research has associated Notch signaling biology because its signaling maintains an un­ and STAT3 activation with differentiation to a differentiated progenitor population.2,3 However, glial cell fate.5­7 This is in apparent contrast to a the exact mechanism by which Notch prevents Notch­dependent preservation of pluripotency. differentiation to prolong self­renewal and pluri­ The discrepancy may be explained by different potency, and its manipulation for therapeutic phosphorlyation sites. Rather than the previously applications, has only recently been proposed reported phosphorlyation of STAT3 (Tyr705) that ® (Figure 1). drives glial cell fate, 7 Androutsellis­Theotokis et al. Notch continued on page 5 MMP-12 in Smoking-Related Pulmonary Disease Chronic obstructive pulmonary disease (COPD), the fifth leading Some elements of COPD pathogenesis precede macrophage or cause of death worldwide, is estimated by the World Health Organ­ neutrophil accumulation. Studies on airway cells in vitro bypass the ization (WHO) to affect 80 million people.1 Cigarette smoking is the influence of inflammatory cells and show direct effects of smoke or major risk factor for COPD, which includes both emphysema and smoke condensates. For example, the oxidative effects of smoke chronic bronchitis, also called small airway disease. In emphysema, induce MMP­12 expression via a TNF­a­dependent pathway in peripheral air spaces in the lung are enlarged and walls of bronchioles cultured airway­like epithelia.7 Oxidants are also involved in release and alveoli are destroyed. Chronic bronchitis, which may occur con­ of TGF­b from latency in tracheal explants.8 Active TGF­b is likely to currently with emphysema, includes airway wall repair­induced fi­ mediate fibrogenic airway remodeling, an effect that is blocked in brosis.1 Inflammation, proteinase imbalance, oxidative stress, and MMP­12­deficient mice.8 Similarly, apoptotic pathways induced by apoptosis all appear to be interwoven in the pathogenesis of COPD, either TGF­b or Fas (CD95) may cause lung fibrosis that can be and the matrix metalloproteinase MMP­12 plays a role in each of ameliorated by deletion of MMP­12.9,10 Human airway smooth muscle these processes (Figure 1). cells have also been shown to contribute active MMP­12 in response to IL­1b a 11 Disruption of the balance between proteolytic enzymes, such as elas­ and TNF­ . tases and their inhibitors, has long been considered the major cause A pivotal study showed that deletion of mouse MMP­12 abrogates of COPD.2 This protease­antiprotease imbalance is now thought to development of cigarette smoke­induced COPD.12 Since then, other be caused by chronic inflammation.2 Macrophage elastase MMP­12 studies have shown that deletion or inhibition of neutrophil elastase, (inhibited by TIMP­1) and neutrophil elastase (inhibited by a­1­ TGF­b, or TNF­a substantially reduces lung damage in response to antitrypsin) are the most abundant elastases in the lung. TNFa, which cigarette smoke.3,4,7,8,13 Conversely, naturally occurring human de­ is released from the cell membrane by MMP­12, is the major recruiter ficiency of a­1­antitrypsin, the major human inhibitor of neutrophil of neutrophils to the lung; IFN­g also recruits neutrophils and stim­ elastase, confers susceptibility to COPD.1, 2 It is clear that the entire ulates MMP­12 activity.2­4 Once present, neutrophil elastases and story of COPD pathogenesis involves these and other players in a oxidants secreted in the inflammatory environment mediate much of complex, interwoven cascade. The development of COPD in response the destruction of lung tissue.5 Elastin fragments are also chemotactic, to cigarette smoke is not universal and, when it does occur, varies in recruiting monocytes that differentiate to form alveolar macrophages time of onset for both humans and rodent strains.1,2 This variation that comprise the bulk of the inflammatory cells accumulating in the likely results from interaction of genetic influences with environment. interstitium, septum, and alveolar airspaces in emphysema.6 One example is the increased susceptibility to COPD in smokers that have specific polymorphisms in both human MMP­1 and MMP­12.14 References Irritants 1. GOLD Executive Summary (2006) http://www.goldcopd.com Oxidants 2. Elias, J. A. et al. (2006) Proc. Am. Thorac. Soc. 3:494. Monocytes 3. Churg, A. et al. (2003) Am. J. Respir. Crit. Care Med. 167:1083. Cigarette Smoke Elastin Fragments 4. Churg, A. et al. (2004) Am. J. Respir. Crit. Care Med. 170:492. 5. Lucattelli, M. et al. (2005) Respir. Res. 6:83. 6. Houghton, A. M. et al. (2006) J. Clin. Invest. 116:753. 7. Lavigne, M. C. & M. J. Eppihimer (2005) Biochem. Biophys. Res. Alveoloar TNF-α Commun. 330:194. MMP-12 Macrophages TNF-α 8. Wang, R. D. et al. (2005) Am. J. Respir. Cell Mol. Biol. 33:387. release 9. Kang, H.­R. et al. (2007) J. Biol. Chem. 282:7723. 10. Matute­Bello, G. et al. (2007) Am. J. Respir. Crit. Care Med., April 9 TIMP-1 Smooth Muscle α-1-AT [Epub ahead of print] and Epithelial tissue 11. Xie, S. et al. (2005) Respir. Res. 6:148. Neutrophils 12. Hautamaki, R. D. et al. (1997) Science 227:2002. TGF-β activation 13. Wright, J. L. et al. (2007) Am. J. Physiol. Lung Cell Mol. Physiol. Neutrophil 292:L125. Apoptosis Elastase 14. Joos, L. et al. (2002) Hum. Mol. Genet. 11:569. Airway repair and remodeling This symbol denotes references that cite the use of our products. Fibrogenesis Airway Damage Figure 1. MMP­12 is produced by alveolar macrophages, smooth Chronic Bronchitis Emphysema muscle cells, and epithelia in response to cigarette smoke. It is a key molecule in the recruitment of inflammatory cells, release of TNF­a, and pathways downstream of TGF­b activation. These activities lead to the airway damage, fibrogenesis, repair, and remodeling that are the hall­ marks of COPD. COPD 2 For research use only. Not for use in diagnostic procedures. Regulation of VE-Cadherin and VEGF R2 by VEGF VE­Cadherin and VEGF R2 are transmembrane It was recently reported that VEGF R2 signal­ adhesion.8 TNF­a also promotes vascular glycoproteins that are expressed in the ad­ ing is enhanced by endocytosis. Interesting­ permeability by inducing Fyn­dependent herens junctions between vascular endo­ ly, VE­Cadherin was shown to play an inhibit­ tyrosine phosphorylation of VE­Cadherin.9 thelial cells (EC). VE­Cadherin interacts ho­ ory role in this process. By binding to VEGF Lastly, exposure of endothelium to oxidized mophilically between neighboring cells to R2, VE­Cadherin prevents VEGF R2 en­ LDL promotes VE­Cadherin internalization provide strength to the endothelium. VE­ docytosis. This favors inactivation by a junc­ and increased monocyte transendothelial Cadherin adhesion is reduced during angio­ tion­associated, transmembrane tyrosine migration.10 phosphatase, called DEP­1.5 genesis and leukocyte extravasation, two When clathrin­ These advances in the understanding of the processes that require decreased EC attach­ dependent internalization transports phos­ interactions between VE­Cadherin and VEGF ment. It is well established that adherens phorylated VEGF R2 to endosomal vesicles, R2 clarify how the adherens junction is junction integrity is regulated by VE­Cadher­ uninterrupted VEGF R2 signaling is made regulated in response to VEGF stimulation.