Purinergic modulation of microglial cell activation

Microglial cells are resident macrophages in the brain and their activation is an important part of the brain immune response and the pathology of the major CNS diseases. Microglial activation is triggered by pathological signals and is characterized by morphological changes, proliferation, phagocytosis and the secretion of various cytokines and inflammatory mediators, which could be both destructive and protective for the nervous tissue. Purines are one of the most important mediators which regulate different aspects of microglial function. They could be released to the extracellular space from neurons, astrocytes and from the microglia itself, upon physiological neuronal activity and in response to pathological stimuli and cellular damage. Microglial activation is regulated by various subtypes of nucleotide (P2X, P2Y) and adenosine (A1, A2A and A3) receptors, which control ionic conductances, membrane potential, gene transcription, the production of inflammatory mediators and cell survival. Among them, the role of P2X7 receptors is especially well delineated, but P2X4, various P2Y, A1, A2A and A3 receptors also powerfully participate in the microglial response. The pathological role of microglial purine receptors has also been demonstrated in disease models; e.g., in ischemia, sclerosis multiplex and neuropathic pain. Due to their upregulation and selective activation under pathological conditions, they provide new avenues in the treatment of neurodegenerative and neuroinflammatory illnesses

Ras-association domain of sorting nexin 27 is critical for regulating expression of GIRK potassium channels

G protein-gated inwardly rectifying potassium (GIRK) channels play an important role in regulating neuronal excitability. Sorting nexin 27b (SNX27b), which reduces surface expression of GIRK channels through a PDZ domain interaction, contains a putative Ras-association (RA) domain with unknown function. Deleting the RA domain in SNX27b (SNX27b-DRA) prevents the down-regulation of GIRK2c/GIRK3 channels. Similarly, a point mutation (K305A) in the RA domain disrupts regulation of GIRK2c/GIRK3 channels and reduces H-Ras binding in vitro. Finally, the dominant-negative H-Ras (S17N) occludes the SNX27b-dependent decrease in surface expression of GIRK2c/GIRK3 channels. Thus, the presence of a functional RA domain and the interaction with Ras-like G proteins comprise a novel mechanism for modulating SNX27b control of GIRK channel surface expression and cellular excitability

Erratum: Comparison of IgE-Binding Capacity, Cross-Reactivity and Biological Potency of Allergenic Non-Specific Lipid Transfer Proteins from Peach, Cherry and Hazelnut

<i>Background:</i> Whether the observed clinical pattern of non-specific lipid transfer protein (nsLTP)-mediated food allergies is attributable to a primary sensitization by Pru p 3 from peach and subsequent cross-reactivity with Rosaceae- and non-Rosaceae-derived foods expressing homologous allergens is still unclear. <i>Objective:</i> To investigate the allergenic properties of nsLTPs from Rosaceae and non-Rosaceae foods. <i>Methods:</i> In peach-, cherry- or hazelnut-allergic patients, prevalence of sensitization, IgE-binding capacity, cross-reactivity and allergenic potency of Pru p 3 was compared with Pru av 3 (cherry) and Cor a 8 (hazelnut). <i>Results:</i> Frequency of sensitization to corresponding nsLTPs was 88, 85, and 77% in peach-, hazelnut- and cherry-allergic patients, respectively. Concomitant allergic reactions to cherry and hazelnut were reported in 51 and 44% of peach-allergic patients, respectively. In contrast to cherry allergy, hazelnut allergy was not strictly associated to peach allergy. Sensitization to Cor a 8 or Pru av 3 was strongly correlated with IgE reactivity to Pru p 3, even when subjects tolerated peach. Specific IgE was highest for Rosaceae LTPs, and cross-inhibition experiments confirmed a stronger IgE-binding capacity of Pru p 3 than Cor a 8. The biological potency of Pru p 3 and Pru av 3 was similar but stronger for both nsLTPs than that of Cor a 8. <i>Conclusion:</i> Clinical cross-reactivity of food-allergic patients in the Mediterranean area is likely attributed to a primary sensitization to Pru p 3 and serological cross-reactivity with homologous food nsLTPs. In comparison to Cor a 8, Rosaceae nsLTPs showed a stronger IgE-binding capacity and allergenic potency indicating a different epitope pattern

The CREATE Project: Development of certified reference materials for allergenic products and validation of methods for their quantification

Allergen extracts have been used for diagnosis and treatment of allergy for around 100 years. During the second half of 20th century, the notion increasingly gained foothold that accurate standardization of such extracts is of great importance for improvement of their quality. As a consequence, manufacturers have implemented extensive protocols for standardization and quality control. These protocols have overall IgE-binding potencies as their focus. Unfortunately, each company is using their own in-house reference materials and their own unique units to express potencies. This does not facilitate comparison of different products. During the last decades, most major allergens of relevant allergen sources have been identified and it has been established that effective immunotherapy requires certain minimum quantities of these allergens to be present in the administered maintenance dose. Therefore, the idea developed to introduce major allergens measurements into standardization protocols. Such protocols based on mass units of major allergen, quantify the active ingredients of the treatment and will at the same time allow comparison of competitor products. In 2001, an EU funded project, the CREATE project, was started to support introduction of major allergen based standardization. The aim of the project was to evaluate the use of recombinant allergens as reference materials and of ELISA assays for major allergen measurements. This paper gives an overview of the achievements of the CREATE projec