The P2X7 receptor is a trimeric ATP-gated cation channel found predominantly, but not exclusively, on immune cells. P2X7 activation results in a number of downstream events, including the release of proinflammatory mediators and cell death and proliferation. As such, P2X7 plays important roles in various inflammatory, immune, neurologic and musculoskeletal disorders. This review focuses on the use of P2X7 antagonists in rodent models of neurologic disease and injury, inflammation, and musculoskeletal and other disorders. The cloning and characterization of human, rat, mouse, guinea pig, dog, and Rhesus macaque P2X7, as well as recent observations regarding the gating and permeability of P2X7, are discussed. Furthermore, this review discusses polymorphic and splice variants of P2X7, as well as the generation and use of P2X7 knockout mice. Recent evidence for emerging signaling pathways downstream of P2X7 activation and the growing list of negative and positive modulators of P2X7 activation and expression are also described. In addition, the use of P2X7 antagonists in numerous rodent models of disease is extensively summarized. Finally, the use of P2X7 antagonists in clinical trials in humans and future directions exploring P2X7 as a therapeutic target are described.

The P2X₇ receptor is a ligand-gated cation-selective channel that mediates ATP-induced apoptosis of cells of the immune system. We and others have shown that P2X₇ is nonfunctional both in lymphocytes and monocytes from some subjects. To study a possible genetic basis we sequenced DNA coding for the carboxyl-terminal tail of P2X₇. In 9 of 45 normal subjects a heterozygous nucleotide substitution (1513A→C) was found, whereas 1 subject carried the homozygous substitution that codes for glutamic acid to alanine at amino acid position 496. Surface expression of P2X₇ on lymphocytes was not affected by this E496A polymorphism, demonstrated both by confocal microscopy and immunofluorescent staining. Monocytes and lymphocytes from the E496A homozygote subject expressed nonfunctional receptor, whereas heterozygotes showed P2X₇ function that was half that of germline P2X₇. Results of transfection experiments showed that the mutant P2X₇ receptor was nonfunctional when expressed at low receptor density but regained function at a high receptor density. This density dependence of mutant P2X₇ function was also seen on differentiation of fresh monocytes to macrophages with interferon-γ, which up-regulated mutant P2X₇ and partially restored its function. P2X₇-mediated apoptosis of lymphocytes was impaired in homozygous mutant P2X₇ compared with germline (8.6versus 35.2%). The data suggest that the glutamic acid at position 496 is required for optimal assembly of the P2X₇receptor.

This paper presents an inertial microfluidic device with a simple serpentine micro-channel to continuously separate particles with high performance. Separation of micro/nano-particles has a variety of potential applications in biomedicine and industry. Among the existing separation technologies, a label-free technique without the use of antibody affinity, filter or centrifugation is highly desired to ensure minimal damage and alteration to the cells. Inertial microfluidics utilising hydrodynamic forces to separate particles is one of the most suitable label-free technologies with a high throughput. Our separation concept relies on size-based differential equilibrium positions of the particles perpendicular to the flow. Highly efficient separation is demonstrated with particles of different sizes. The results indicate that the proposed device has an integrative advantage to the existing microfluidic separation techniques, taking accounts of purity, efficiency, parallelizability, footprint, throughput and resolution. Our device is expected to be a good alternative to conventional separation methods for sample preparation and clinical diagnosis.

Rationale: Genetic variation influences susceptibility to clinical tuberculosis (TB). Activation of the P2X7 receptor on human macrophages induces killing of mycobacteria. We have identified polymorphisms in the P2X7 gene that markedly reduce this killing. Objective: To determine if polymorphisms in P2X7 are associated with increased risk of TB, the prevalence of four polymorphisms was assessed in individuals from Southeast Asia, where the majority of patients with TB in our study originate. The association of these polymorphisms with clinical TB was subsequently investigated in two separate case-control cohorts and the function of P2X7 was assessed in subjects from one cohort. Methods: Genotyping of P2X7 polymorphisms was performed from subjects in a nested case-control study of a longitudinal refugee cohort and a separate case-control study. The functional capacity of P2X7 was investigated by measuring ATP-mediated mycobacterial killing and apoptosis. Results: Only the 1513A-C polymorphism was present in Southeast Asians and the allele was associated with reduced killing of Mycobacterium tuberculosis. The 1513C allele was strongly associated with extrapulmonary, but not pulmonary, TB in the first (odds ratio, 3.8; 95% confidence interval, 1.6–9.0) and second cohorts (odds ratio, 3.7; 95% confidence interval, 1.7–8.0). ATP-mediated killing of mycobacteria was ablated in macrophages from subjects homozygous for the 1513C allele and significantly impaired in macrophages from heterozygous subjects. There was strong correlation between the degree of mycobacterial killing and ATP-induced apoptosis. Conclusions: The 1513C allele increases susceptibility to extrapulmonary TB, and this defect is associated with the reduction in the capacity of macrophages to kill M. tuberculosis.