Interleukin-1α Activity in Necrotic Endothelial Cells Is Controlled by Caspase-1 Cleavage of Interleukin-1 Receptor-2: IMPLICATIONS FOR ALLOGRAFT REJECTION*

Inflammation is a key instigator of the immune responses that drive atherosclerosis and allograft rejection. IL-1α, a powerful cytokine that activates both innate and adaptive immunity, induces vessel inflammation after release from necrotic vascular smooth muscle cells (VSMCs). Similarly, IL-1α released from endothelial cells (ECs) damaged during transplant drives allograft rejection. However, IL-1α requires cleavage for full cytokine activity, and what controls cleavage in necrotic ECs is currently unknown. We find that ECs have very low levels of IL-1α activity upon necrosis. However, TNFα or IL-1 induces significant levels of active IL-1α in EC necrotic lysates without alteration in protein levels. Increased activity requires cleavage of IL-1α by calpain to the more active mature form. Immunofluorescence and proximity ligation assays show that IL-1α associates with interleukin-1 receptor-2, and this association is decreased by TNFα or IL-1 and requires caspase activity. Thus, TNFα or IL-1 treatment of ECs leads to caspase proteolytic activity that cleaves interleukin-1 receptor-2, allowing IL-1α dissociation and subsequent processing by calpain. Importantly, ECs could be primed by IL-1α from adjacent damaged VSMCs, and necrotic ECs could activate neighboring normal ECs and VSMCs, causing them to release inflammatory cytokines and up-regulate adhesion molecules, thus amplifying inflammation. These data unravel the molecular mechanisms and interplay between damaged ECs and VSMCs that lead to activation of IL-1α and, thus, initiation of adaptive responses that cause graft rejection.     

A new method for cell permeabilization reveals a cytosolic protein requirement for Ca2+ -activated secretion in GH3 pituitary cells

Ca2+ is a major regulator of exocytosis in secretory cells, however, the biochemical mechanisms underlying regulation remain to be identified. To render the secretory apparatus accessible for biochemical studies, we have developed a cell permeabilization method (cell cracking) which utilizes mechanical shear. GH3 pituitary cells subjected to cracking were permeable to macromolecules but retained a normal cytoplasmic ultrastructure including secretory granules. Incubation of the permeable cells at 30-37 degrees C with 0.1-1.0 microM Ca2+ and millimolar MgATP resulted in the release of the secretory proteins, prolactin (PRL) and a proteoglycan, but not lysosomal enzymes. Extensively washed permeable cells were incapable of releasing PRL in response to Ca2+ and MgATP addition. However, addition of cytosol was found to restore Ca2+-activated, MgATP-dependent PRL release. The cytosolic factor responsible for activity was thermolabile and protease sensitive. The protein was partially purified, and its molecular mass was estimated to be equivalent to that of a globular protein of 200-350 kDa by molecular sieve chromatography. Inhibitors of calmodulin or protein kinase C (trifluroperazine, calmidazolium, H-7) failed to inhibit Ca2+-activated PRL release, and the required cytosolic protein could not be replaced by purified calmodulin, calmodulin-dependent protein kinase II, protein kinase C, or calpactin I. Further purification and characterization of the cytosolic protein should reveal the nature of biochemical events involved in regulated secretory exocytosis.     

Species richness of herbivores on exotic host plants increases with time since introduction of the host

Aim Species richness of insect herbivores feeding on exotic plants increases with abundance as well as range size of the host in the area of introduction. The formation of these herbivore assemblages requires a certain amount of time, and the richness of insect faunas should also increase with the length of time an exotic plant has been present in the introduced range. Location Central Europe. Methods We analysed the variation in species richness of leaf‐chewing Lepidoptera larvae and sap‐sucking Auchenorrhyncha (Hemiptera) associated with 103 exotic woody plant species in Germany in relation to time since introduction, range size, growth form (trees versus shrubs), biogeographical origin (distance from Central Europe) and taxonomic isolation of the host plant (presence or absence of a native congener in the introduced area). Results Using simple correlation analyses we found for Lepidoptera and Auchenorrhyncha that species richness increased with time since introduction of the host plant. For the Lepidoptera the increase of species richness with time since introduction remained significant even after removing the effects of all other independent variables. Main conclusions Our results provide some evidence that assemblages of insects on exotic plants do not reach saturation within a time scale of few hundred years. This contrasts with previous findings for crop plants.     

Protective effects of total fraction of avocado/soybean unsaponifiables on the structural changes in experimental dog osteoarthritis: inhibition of nitric oxide synthase and matrix metalloproteinase-13

Introduction  

The aims of this study were, first, to investigate the in vivo effects of treatment with avocado/soybean unsaponifiables on the development of osteoarthritic structural changes in the anterior cruciate ligament dog model and, second, to explore their mode of action.     

Predation of birds in mist nets by callitrichids (primates): how to prevent similar events

We report predation of four birds while caught in mist nets and recommend some means of prevention. Two birds were attacked by Callitrhix jacchus and one by Saguinus midas. The predator in the fourth case was unidentified. These cases were relatively rare, affecting 0.4–4.4% of the captured birds. Two of the predated birds were caught more than 1 m above the ground and may have been accessed from branches. The other two were caught close to the ground. Reducing time intervals between net checks and cutting off branches close to nets may reduce bird predation in mist nets.