Intranasal LAG3 antibody infusion induces microglia-dependent antidepressant effect by mobilizing astrocytic P2Y1R-mediated BDNF synthesis in the hippocampus.

Stimulation of microglia leads to a rapid antidepressant effect by triggering astrocytic P2Y1Rs and promoting BDNF-mediated neurogenesis in the hippocampus.

The immunoregulator β-glucan produces antidepressant effects through microglia-mobilized astrocytic P2Y1R-BDNF signaling in the dentate gyrus.

Intranasal LAG3 antibody infusion induces a rapid antidepressant effect via the hippocampal ERK1/2-BDNF signaling pathway in chronically stressed mice

β-glucan, a specific immuno-stimulant, produces rapid antidepressant effects by stimulating ERK1/2-dependent synthesis of BDNF in the hippocampus

In animal cells, adenosine triphosphate (ATP) serves not only as an energy source but also as an extracellular signaling molecule, a ligand for purinergic cell surface receptors. A role for extracellular ATP in plants is also beginning to emerge, and Chivasa et al. report that extracellular ATP is required for plant cell viability and that depletion of ATP may be one mechanism by which the process of pathogen-induced hypersensitive cell death is triggered (see commentary by Eckardt). Arabidopsis cells in culture released ATP into the medium. Cell-impermeant enzymes that consumed or metabolized ATP, such as hexokinase or apyrase, depleted extracellular ATP and caused cell death in cultures of Arabidopsis and maize. The nonhydrolyzable ATP analog βγ-methyleneadenosine 5′-triphosphate (AMP-PCP) also decreased cell viability. Application of apyrase, hexokinase, or AMP-PCP also caused localized cell death in leaves of Arabidopsis , tobacco, and bean plants. The entire Arabidopsis plant was susceptible to death if grown with hexokinase or AMP-PCP in the medium (hydroponically grown plants) or nutrient agar. Fumonisin B1 (FB1) is an elicitor produced by the maize pathogen Fusarium moniliforme , which causes programmed cell death and activation of the plant defense response. Arabidopsis cell cultures grown in the presence of FB1 had decreased extracellular ATP, and the decline preceded loss of membrane integrity. Addition of ATP rescued the cells from FB1-induced death, as did addition of other nucleoside triphosphates, which prevented ATP from decreasing by competing for ATP-degrading enzymes. Exogenous ATP also rescued Arabidopsis plants grown in the presence of FB1 from death, but did not rescue the plants from the growth retardation effects of FB1, suggesting that ATP selectively protects against FB1-mediated cell death. Mass spectrometry revealed that the abundance of several (34) intracellular proteins, including several implicated in the stress response, was altered by depletion of extracellular ATP. Thus, extracellular ATP appears to be one of the signals that inhibits what is known as the "default death pathway" in plants and connects cell viability to the pathogen elicitor-triggered cell death response. The mechanism by which ATP exerts this effect--for example, through phosphorylation of an extracellular protein, through serving as a cofactor in the formation of an extracellular complex, or through serving as a ligand for an extracellular receptor--remains to be determined. S. Chivasa, B. K. Ndimba, W. J. Simon, K. Lindsey, A. R. Slabas, Extracellular ATP functions as an endogenous external metabolite regulating plant cell viability. Plant Cell 17 , 3019-3034 (2005). [Abstract] [Full Text] N. A. Eckardt, Ins and outs of programmed cell death and toxin action. Plant Cell 17 , 2849-2851 (2005). [Full Text]

A preceding hypoxic insult can sensitize the cells or the organism to a subsequent, second insult. The aim of the present study was to investigate the molecular mechanism of this phenomenon (often termed ‘two-hit’ injury paradigm), in an in vitro model of hypoxia/oxidative stress injury in A549 epithelial cells, with special emphasis on the role of the nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) in the process. Pre-exposure of the cells to 24 h hypoxia significantly reduced intracellular glutathione (GSH) levels, reduced mitochondrial activity and adenosine triphosphate (ATP) levels. However pre-exposure to hypoxia failed to induce any change in PARP-1 expression and activation, DNA single-strand breaks or plasma membrane integrity. Pre-exposure to hypoxia markedly increased the sensitivity of the cells to subsequent oxidative stress-induced DNA damage. Hydrogen peroxide (H2O2) induced a concentration-dependent increase in DNA breakage, PARP activation, depletion of intracellular ATP, inhibition of mitochondrial activity and two distinct parameters that quantify the breakdown of plasma membrane integrity (propidium iodide uptake or lactate dehydrogenase release). PARP-1 activation played a significant role in the H2O2-induced cell death response because PARP activation, depletion of intracellular ATP, inhibition of mitochondrial activity, and the breakdown of plasma membrane integrity were attenuated in cells with permanently silenced PARP-1. Based on measurement of the endogenous antioxidant GSH, we hypothesized that the mechanism of hypoxia-mediated enhancement of H2O2 involves depletion of the GSH during the hypoxic period, which renders the cells more sensitive to a subsequent DNA single-strand break elicited by H2O2. DNA strand breakage then activates PARP-1, leading to the inhibition of mitochondrial function, depletion of ATP and cell necrosis. PARP-1 deficiency protects against the cytotoxicity, to a lesser degree, by protecting against GSH depletion during the hypoxic period, and, to a larger degree, by maintaining mitochondrial function and preserving intracellular ATP levels during the subsequent oxidative stress period.

Endothelial cells under physiological conditions can alter energy balance by alteration in synthesis, metabolism and transport of adenosine triphosphate (ATP), which failed during endothelial cell dysfunction. ATP depleted endothelial cells are unable to perform their physiological functions as energy dependent protein secretion. Isolated human umbilical vein endothelial cells (HUVEC) from fresh umbilical cords were treated with 10 mM 2-deoxyglucose and 0.1 pg/ml of oligomycin for 6 h to induce ATP depletion. Nitric oxide (NO), von Willebrand factor (vWF), lactate dehydrogenase (LDH) release and trypan-blue exclusion were compared between treated and untreated cells. We observed a slight decrease in nitric oxide levels (P = 0.09) and vWF (P = 0.395) in the setting of 49.36% ATP depletion. There was no significant change in LDH release and cell viability between treated and untreated cells (P > 0.05). Since vWF exocytosis is an energy consuming process, decreased secretion of vWF in the isolated near-half percent of ATP depletion is not seemingly at odds. The application of vWF exocytosis fades as a candidate marker for ATP depletion induced injury, in cultured endothelial cells. Nitric oxide level and vWF secretion are not candidate markers of endothelial cell dysfunction in isolated partial ATP- depleted HUVECs. Measures such as arachidonic acid synthesis may be better alternatives.   Key words: Endothelial cell dysfunction, adenosine triphosphate (ATP) depletion, nitric oxide, von Willebrand factor (vWF).

Intrahepatic bile ducts (BD) are a critical target of injury in the postischemic liver. Decreased vascular perfusion causes characteristic changes in the morphology of the ductular epithelia including a loss of secondary membrane structures and a decrease in plasma membrane surface area. Using adenosine triphosphate (ATP) depletion of cultured normal rat cholangiocytes (NRC) to model ischemic ducts, the present studies examined the fate of apical membrane proteins to determine whether membrane recycling might contribute to rapid functional recovery. Apical proteins, including gamma-glutamyl transpeptidase (GGT), Na(+)-glucose cotransporter (SGLT1), and apically biotinylated proteins, were not shed into the luminal space during ATP depletion. Instead, labeling of surface proteins after ATP depletion showed a significant decrease in GGT and SGLT1, consistent with membrane internalization. Similarly, z-axis confocal microscopy of biotinylated apical proteins also showed protein internalization. During ATP recovery, SGLT1 transport activity remained profoundly depressed even after 24 hours of recovery, indicating that the function of the internalized apical proteins is not rapidly recovered. These studies suggest that the membrane internalization in ATP-depleted cholangiocytes is a unidirectional process that contributes to prolonged functional deficits after restoration of normal cellular ATP levels. This sustained decrease in transport capacity may contribute to the development of ductular injury in postischemic livers.

Using 45Ca, indo1, and quin2, calcium uptake was measured in isolated quiescent adult rat heart cells under different metabolic conditions. Exposure of cells in a medium containing 1 mM CaCl2 to rotenone and uncoupler resulted in adenosine triphosphate (ATP) depletion from 17.08 +/- 2.26 to 0.63 +/- 0.11 nmol/mg within 8 minutes, and the cells went into contracture. In this time, the cells lost 1.65 +/- 0.1 nmol Ca/mg of total rapidly exchangeable cellular calcium, and the level of free cytosolic calcium as measured by indo1 rose from 47.4 +/- 16.3 nM to 79.8 +/- 27.6 nM. The subsequent rate of rise of intracellular free calcium concentration was just 4 nM/min for at least 40 minutes. Therefore, we investigated the effect of ATP depletion on the rate of calcium entry. In cells loaded with sodium by ouabain treatment without calcium, the initial rate of calcium influx on calcium addition was inhibited by 82-84% when cellular ATP was depleted, as measured by 45Ca or indo1. Quin2 also showed a strong inhibition of calcium influx by ATP depletion, but itself also caused a strong inhibition of calcium influx. The rate of calcium influx declined even further in ATP-depleted cells after the initial influx: Between 1 and 12 minutes after calcium addition, the residual 45Ca uptake rate of the first minute was inhibited by an additional 90%. We conclude that ATP depletion per se does not quickly elevate cytoplasmic free calcium and that such an elevation is prevented by a very strong inhibition of the rate of calcium entry.

Prior heat stress inhibits apoptosis in adenosine triphosphate-depleted renal tubular cells

Cigarette smoke augments asbestos-induced alveolar epithelial cell injury: role of free radicals

Expression of mutant N-terminal huntingtin fragment (htt552-100Q) in astrocytes suppresses the secretion of BDNF

Intestinal ischemia-reperfusion is a common clinical event associated with both clinical and experimental distant organ injury. In particular, the pulmonary microvasculature appears to be susceptible to injury resulting from systemic inflammatory mediator activation. This study was designed to evaluate the hypothesis that noncellular humoral factors associated with intestinal ischemia-reperfusion result in pulmonary endothelial cell adenosine triphosphate (ATP) depletion. Male Sprague-Dawley rats had intestinal ischemia induced by microvascular clip occlusion of the superior mesenteric artery (SMA) for 120 minutes. Reperfusion resulted from superior mesenteric artery clip removal. After reperfusion for 0, 15, or 30 minutes, plasma samples were obtained from the portal vein. Monolayers of cultured rat pulmonary artery endothelial cells then were incubated with the plasma samples. Adenosine triphosphate levels were determined using a luciferin-luciferase assay. A 51Cr-release assay using labeled endothelial cells was performed under identical conditions to assess cytotoxicity. Potential mechanisms of ATP depletion were evaluated by analysis of cellular energy charge and assessment of microfilament architecture. Endothelial cell ATP levels decreased from 2.23 +/- 0.16 x 10(-11) moles/microgram DNA in sham preparations to 1.23 +/- 0.09 x 10(-11) moles/microgram DNA (p < 0.001) after 4 hours in plasma from animals undergoing 120 minutes of intestinal ischemia. For plasma obtained after 15 minutes of reperfusion, the decrease in cellular ATP concentration persisted (1.23 +/- 0.27 x 10(-11) moles/microgram DNA, p < 0.001 vs. sham). After 30 minutes' reperfusion, cellular ATP levels increased only slightly after the 4-hour incubation (1.39 +/- 0.26 x 10(-11) moles/microgram DNA, p < 0.005 vs. sham). No significant cytotoxic injury occurred in any group when compared with controls. Cellular energy charge was unchanged, and microfilament architecture was preserved. These data confirm the hypothesis that humoral factors, independent of the neutrophil, result in endothelial cell ATP depletion without metabolic inhibition or cell death. Depletion of energy stores by noncellular humoral factors may represent an early event that predisposes the cell to more severe injury by other mediators of the endogenous inflammatory response.

Definition of a Bidirectional Activity-Dependent Pathway Involving BDNF and Narp.

Glutamate excitotoxicity is implicated in the pathogenesis of numerous diseases, such as stroke, traumatic brain injury, and Alzheimer’s disease, for which insulin resistance is a concomitant condition, and intranasal insulin treatment is believed to be a promising therapy. Excitotoxicity is initiated primarily by the sustained stimulation of ionotropic glutamate receptors and leads to a rise in intracellular Ca2+ ([Ca2+]i), followed by a cascade of intracellular events, such as delayed calcium deregulation (DCD), mitochondrial depolarization, adenosine triphosphate (ATP) depletion that collectively end in cell death. Therefore, cross-talk between insulin and glutamate signaling in excitotoxicity is of particular interest for research. In the present study, we investigated the effects of short-term insulin exposure on the dynamics of [Ca2+]i and mitochondrial potential in cultured rat cortical neurons during glutamate excitotoxicity. We found that insulin ameliorated the glutamate-evoked rise of [Ca2+]i and prevented the onset of DCD, the postulated point-of-no-return in excitotoxicity. Additionally, insulin significantly improved the glutamate-induced drop in mitochondrial potential, ATP depletion, and depletion of brain-derived neurotrophic factor (BDNF), which is a critical neuroprotector in excitotoxicity. Also, insulin improved oxygen consumption rates, maximal respiration, and spare respiratory capacity in neurons exposed to glutamate, as well as the viability of cells in the MTT assay. In conclusion, the short-term insulin exposure in our experiments was evidently a protective treatment against excitotoxicity, in a sharp contrast to chronic insulin exposure causal to neuronal insulin resistance, the adverse factor in excitotoxicity.