The HL-60 human promyelocytic cell line constitutes an effective in vitro model for evaluating toxicity, oxidative stress and necrosis/apoptosis after exposure to black carbon particles and 2.45 GHz radio frequency.

The cellular and molecular mechanisms by which atmospheric pollution from particulate matter and/or electromagnetic fields (EMFs) may prove harmful to human health have not been extensively researched. We analyzed whether the combined action of EMFs and black carbon (BC) particles induced cell damage and a pro-apoptotic response in the HL-60 promyelocytic cell line when exposed to 2.45 GHz radio frequency (RF) radiation in a gigahertz transverse electromagnetic (GTEM) chamber at sub-thermal specific absorption rate (SAR) levels. RF and BC induced moderately significant levels of cell damage in the first 8 or 24 h for all exposure times/doses and much greater damage after 48 h irradiation and the higher dose of BC. We observed a clear antiproliferative effect that increased with RF exposure time and BC dose. Oxidative stress or ROS production increased with time (24 or 48 h of radiation), BC dose and the combination of both. Significant differences between the proportion of damaged and healthy cells were observed in all groups. Both radiation and BC participated separately and jointly in triggering necrosis and apoptosis in a programmed way. Oxidative-antioxidant action activated mitochondrial anti-apoptotic BCL2a gene expression after 24 h irradiation and exposure to BC. After irradiation of the cells for 48 h, expression of FASR cell death receptors was activated, precipitating the onset of pro-apoptotic phenomena and expression and intracellular activity of caspase-3 in the mitochondrial pathways, all of which can lead to cell death. Our results indicate that the interaction between BC and RF modifies the immune response in the human promyelocytic cell line and that these cells had two fates mediated by different pathways: necrosis and mitochondria-caspase dependent apoptosis. The findings may be important in regard to antimicrobial, inflammatory and autoimmune responses in humans.

Radiofrequency at 2.45 GHz increases toxicity, pro-inflammatory and pre-apoptotic activity caused by black carbon in the RAW 264.7 macrophage cell line.

Environmental factors such as air pollution by particles and/or electromagnetic fields (EMFs) are studied as harmful agents for human health. We analyzed whether the combined action of EMF with fine and coarse black carbon (BC) particles induced cell damage and inflammatory response in RAW 264.7 cell line macrophages exposed to 2.45 GHz in a gigahertz transverse electromagnetic (GTEM) chamber at sub-thermal specific absorption rate (SAR) levels. Radiofrequency (RF) dramatically increased BC-induced toxicity at high doses in the first 24 h and toxicity levels remained high 72 h later for all doses. The increase in macrophage phagocytosis induced after 24 h of RF and the high nitrite levels obtained by stimulation with lipopolysaccharide (LPS) endotoxin 24 and 72 h after radiation exposure suggests a prolongation of the innate and inflammatory immune response. The increase of proinflammatory cytokines tumor necrosis factor-α, after 24 h, and of interleukin-1ß and caspase-3, after 72 h, indicated activation of the pro-inflammatory response and the apoptosis pathways through the combined effect of radiation and BC. Our results indicate that the interaction of BC and RF modifies macrophage immune response, activates apoptosis, and accelerates cell toxicity, by which it can activate the induction of hypersensitivity reactions and autoimmune disorders.

Orexin neurons as conditional glucosensors: paradoxical regulation of sugar sensing by intracellular fuels.

Central orexin/hypocretin neurons promote wakefulness, feeding and reward-seeking, and control blood glucose levels by regulating sympathetic outflow to the periphery. Glucose itself directly suppresses the electrical activity and cytosolic calcium levels of orexin cells. Recent in vitro studies suggested that glucose inhibition of orexin cells may be mechanistically unusual, because it persists under conditions where glucose metabolism is unlikely. To investigate this further, and to clarify whether background metabolic state regulates orexin cell glucosensing, here we analysed glucose responses of orexin cells in mouse brain slices, in the presence and absence of metabolic inhibitors and physiological energy substrates. Consistent with their documented insensitivity to glucokinase inhibitors, the glucose responses of orexin cells persisted in the presence of the mitochondrial poison oligomycin or the glial toxin fluoroacetate. Unexpectedly, in the presence of oligomycin, the magnitude of the glucose response was significantly enhanced. In turn, 2-deoxyglucose, a non-metabolizable glucose analogue, elicited larger responses than glucose. Conversely, intracellular pyruvate dose-dependently suppressed the glucose responses, an effect that was blocked by oligomycin. The glucose responses were also suppressed by intracellular lactate and ATP. Our new data suggest that other energy substrates not only fail to mimic the orexin glucose response, but paradoxically suppress it in a metabolism-dependent manner. We propose that this unexpected intrinsic property of orexin cells allows them to act as 'conditional glucosensors' that preferentially respond to glucose during reduced background energy levels.

Dissociation between sensing and metabolism of glucose in sugar sensing neurones.

Some of the neurones controlling sleep, appetite and hormone release act as specialized detectors of ambient glucose. Their sugar sensing is conventionally thought to involve glucokinase-dependent metabolism of glucose to ATP, which then alters membrane excitability by modulating ATP-dependent channels or transporters, such as ATP-inhibited K(+) channels (K(ATP)). However, recent studies also provide examples of both glucose-excited (GE) and glucose-inhibited (GI) neurones that sense glucose independently of such metabolic pathways. Two-thirds of hypothalamic GE neurones in primary cultures are also excited by the non-metabolizable glucose analogue alpha-methylglucopyranoside (alpha-MDG), which acts as a substrate for electrogenic (depolarizing) sodium-glucose cotransporter (SGLT). The excitatory responses to both glucose and alpha-MDG are abolished by arresting SGLT activity by sodium removal or the SGLT inhibitor phloridzin. Direct depolarization and excitation by glucose-triggered SGLT activity may ensure that GE neurones continue to sense glucose in 'high-energy' states, when K(ATP) channels are closed. A major class of hypothalamic GI neurones, the orexin/hypocretin cells, also appear to use a non-metabolic sensing strategy. In these cells, glucose-induced hyperpolarization and inhibition are unaffected by glucokinase inhibitors such as alloxan, D-glucosamine, and N-acetyl-D-glucosamine, and mimicked by the non-metabolizable glucose analogue 2-deoxyglucose, but not by stimulating intracellular ATP production with lactate. The dissociation between sensing and metabolism of sugar may allow the brain to predict and prevent adverse changes in extracellular glucose levels with minimal impact on the flow of intracellular fuel.