T-cell activation requires the influx of extracellular calcium, although mechanistic details regarding such activation are not fully defined. Here, we show that P2X(7) receptors play a key role in calcium influx and downstream signaling events associated with the activation of T cells. By real-time PCR and immunohistochemistry, we find that Jurkat T cells and human CD4(+) T cells express abundant P2X(7) receptors. We show, using a novel fluorescent microscopy technique, that T-cell receptor (TCR) stimulation triggers the rapid release of ATP (<100 microM). This release of ATP is required for TCR-mediated calcium influx, NFAT activation, and interleukin-2 (IL-2) production. TCR activation up-regulates P2X(7) receptor gene expression. Removal of extracellular ATP by apyrase or alkaline phosphatase treatment, inhibition of ATP release with the maxi-anion channel blocker gadolinium chloride, or siRNA silencing of P2X(7) receptors blocks calcium entry and inhibits T-cell activation. Moreover, lymphocyte activation is impaired in C57BL/6 mice that express poorly functional P2X(7) receptors, compared to control BALB/c mice, which express fully functional P2X(7) receptors. We conclude that ATP release and autocrine, positive feedback through P2X(7) receptors is required for the effective activation of T cells.

BackgroundSubterranean blind mole rats (Spalax) are hypoxia tolerant (down to 3% O2), long lived (>20 years) rodents showing no clear signs of aging or aging related disorders. In 50 years of Spalax research, spontaneous tumors have never been recorded among thousands of individuals. Here we addressed the questions of (1) whether Spalax is resistant to chemically-induced tumorigenesis, and (2) whether normal fibroblasts isolated from Spalax possess tumor-suppressive activity.ResultsTreating animals with 3-Methylcholantrene (3MCA) and 7,12-Dimethylbenz(a) anthracene/12-O-tetradecanoylphorbol-13-acetate (DMBA/TPA), two potent carcinogens, confirmed Spalax high resistance to chemically induced cancers. While all mice and rats developed the expected tumors following treatment with both carcinogens, among Spalax no tumors were observed after DMBA/TPA treatment, while 3MCA induced benign fibroblastic proliferation in 2 Spalax individuals out of12, and only a single animal from the advanced age group developed malignancy 18 months post-treatment. The remaining animals are still healthy 30 months post-treatment. In vitro experiments showed an extraordinary ability of normal Spalax cultured fibroblasts to restrict malignant behavior in a broad spectrum of human-derived and in newly isolated Spalax 3MCA-induced cancer cell lines. Growth of cancer cells was inhibited by either direct interaction with Spalax fibroblasts or with soluble factors released into culture media and soft agar. This was accompanied by decreased cancer cell viability, reduced colony formation in soft agar, disturbed cell cycle progression, chromatin condensation and mitochondrial fragmentation. Cells from another cancer resistant subterranean mammal, the naked mole rat, were also tested for direct effect on cancer cells and, similar to Spalax, demonstrated anti-cancer activity. No effect on cancer cells was observed using fibroblasts from mouse, rat or Acomys. Spalax fibroblast conditioned media had no effect on proliferation of noncancerous cells.ConclusionsThis report provides pioneering evidence that Spalax is not only resistant to spontaneous cancer but also to experimentally induced cancer, and shows the unique ability of Spalax normal fibroblasts to inhibit growth and kill cancer cells, but not normal cells, either through direct fibroblast-cancer cell interaction or via soluble factors. Obviously, along with adaptation to hypoxia, Spalax has evolved efficient anti-cancer mechanisms yet to be elucidated. Exploring the molecular mechanisms allowing Spalax to survive in extreme environments and to escape cancer as well as to kill homologous and heterologous cancer cells may hold the key for understanding the molecular nature of host resistance to cancer and identify new anti-cancer strategies for treating humans.

Vigorous infusion of normal saline after massive splenic injury resulted in a significant increase in intra-abdominal bleeding and decreased survival time. The hemodynamic response to crystalloid infusion in blunt abdominal trauma is primarily dependent on the severity of injury and the rate of blood loss.