Calcium dependency of interleukin-1 secretion by a chicken macrophage cell line

Chemicals inducing acute irritant contact dermatitis mobilize intracellular calcium in human keratinocytes

Intracellular Ca(2+) increase is a common feature of multiple cellular pathways associated with receptor and channel activation, mediator secretion and gene regulation. We investigated the possibility of using this Ca(2+) signal as a biomarker for a reaction to chemical irritants of normal human keratinocytes (NHK) in submerged primary cell culture. We tested 14 referenced chemical compounds classified as strong (seven), weak (four) or non- (three) irritants in acute irritant contact dermatitis. We found that the strong irritant compounds tested at 20-40 mM induced an intracellular Ca(2+) increase measurable by spectrofluorimetry in an automated test. Weak and non-irritant compounds however did not increase intracellular Ca(2+) concentration. We further investigated the mechanisms by which the amine heptylamine, classified as a R34 corrosive compound, increases intracellular Ca(2+). Heptylamine (20mM) induced an ATP release that persisted in the absence of intra- and extra-cellular Ca(2+). In addition, we found that this ATP activates NHK purinergic receptors that subsequently cause the increase in intracellular Ca(2+) from sarcoplasmic reticular stores. We conclude that measuring the intracellular Ca(2+) concentration in NHK is a suitable and easy way of determining any potential reaction to soluble chemical compounds.

Extracellular ATP and P2X7 receptors in neurodegeneration

Neuronal injury and cell death in the central nervous system (CNS) are underlying features of neurodegenerative disorders. However, our understanding of the fundamental mechanisms involved is still limited. Inflammatory processes mediated by cytokines, and interleukin-1 (IL-1) in particular, play a significant role in neuronal death following pathological insults. Despite this growing area of research, very little is known about the factors regulating the expression, cleavage and release of interleukin-1 in the brain. Recent studies on immune cells demonstrate that extracellular ATP can act as a potent stimulus for the maturation and release of interleukin-1beta, via activation of P2X7 receptors. Stimulation of P2X7 receptors with ATP has dramatic cytotoxic properties and a wider role in neurodegenerative processes is possible. This review discusses the potential involvement of extracellular ATP and P2X7 receptors as regulators of interleukin-1-mediated neuropathologies and thus as a mediator of cell death following pathological insults.

Cytokines of birds: conserved functions--a largely different look

Targeted disruptions of the mouse genes for cytokines, cytokine receptors, or components of cytokine signaling cascades convincingly revealed the important roles of these molecules in immunologic processes. Cytokines are used at present as drugs to fight chronic microbial infections and cancer in humans, and they are being evaluated as immune response modifiers to improve vaccines. Until recently, only a few avian cytokines have been characterized, and potential applications thus have remained limited to mammals. Classic approaches to identify cytokine genes in birds proved difficult because sequence conservation is generally low. As new technology and high throughput sequencing became available, this situation changed quickly. We review here recent work that led to the identification of genes for the avian homologs of interferon-alpha/beta (IFN-alpha/beta) and IFN-gamma, various interleukins (IL), and several chemokines. From the initial data on the biochemical properties of these molecules, a picture is emerging that shows that avian and mammalian cytokines may perform similar tasks, although their primary structures in most cases are remarkably different.

Vanadium stimulates immunological responses of chicks

In a continuation of studies on the interaction of dietary phosphorus (P) and vanadium (V) levels, studies have directed toward an examination of this interaction on the immune system of chicks. Antibody titers to sheep red blood cells (SRBC) were increased at 7 days post-inoculation (PI) by as little as 10 mg V/kg diet in the P-deficient group, while 50 mg V/kg was required in the P-supplemented group. At 14 days PI, only the 50 mg V/kg was significantly higher in both P-deficient and P-supplemented groups. At 21 days PI, vanadium had no significant effect. P-deficiency resulted in a decrease in the percentage of phagocytic macrophages obtained from the abdominal cavity and a decrease in the number of intracytoplasmic SRBC per phagocytic macrophage. These two criteria were increased by vanadium in both the P-deficient and P-supplemented animals. In P-supplemented animals, the CD4/CD8 ratios of lymphocytes obtained from the blood and spleen were increased by the inclusion of 50 mg V/kg diet. The IL-1-like activity of macrophage supernatants was not significantly affected by dietary V, but IL-6 activity was increased. Densitometric analysis of lysates of macrophages isolated from control and V-fed chicks for anti-protein-tyrosinephosphate (PTP) bands indicate that dietary V increased PTP. While the evidence is not clear that there is a P x V interaction in the immune system studies, it is clear that dietary V at the levels used results in a positive immune response of chicks, possibly mediated through increased PTP.