Purinergic responses of calcium-dependent signaling pathways in cultured adult human astrocytes
Bibliographic record
Abstract
BACKGROUND: The properties of Ca2+ signaling mediated by purinergic receptors are intrinsically linked with functional activity of astrocytes. At present little is known concerning Ca2+-dependent purinergic responses in adult human astrocytes. This work has examined effects of purinergic stimulation to alter levels of intracellular Ca2+ in adult human astrocytes. Ca2+-sensitive spectrofluorometry was carried out to determine mobilization of intracellular Ca2+ following adenosine triphosphate (ATP) or 3'-O-(4-benzoyl)benzoyl-ATP (Bz-ATP) stimulation of adult human astrocytes. In some experiments pharmacological modulation of Ca2+ pathways was applied to help elucidate mechanisms of Ca2+ signaling. RT-PCR was also performed to confirm human astrocyte expression of specific purinoceptors which were indicated from imaging studies. RESULTS: The endogenous P2 receptor agonist ATP (at 100 μM or 1 mM) applied in physiological saline solution (PSS) evoked a rapid increase of [Ca2+]i to a peak amplitude with the decay phase of response exhibiting two components. The two phases of decay consisted of an initial rapid component which was followed by a secondary slower component. In the presence of Ca2+-free solution, the secondary phase of decay was absent indicating this prolonged component was due to influx of Ca2+. This prolonged phase of decay was also attenuated with the store-operated channel (SOC) inhibitor gadolinium (at 2 μM) added to standard PSS, suggesting this component was mediated by SOC activation. These results are consistent with ATP activation of P2Y receptor (P2YR) in adult human astrocytes leading to respective rapid [Ca2+]i mobilization from intracellular stores followed by Ca2+ entry through SOC. An agonist for P2X7 receptor (P2X7R), BzATP induced a very different response compared with ATP whereby BzATP (at 300 μM) elicited a slowly rising increase in [Ca2+]i to a plateau level which was sustained in duration. The BzATP-induced increase in [Ca2+]i was not enhanced with lipopolysaccharide pre-treatment of cells as previously found for P2X7R mediated response in human microglia. RT-PCR analysis showed that adult human astrocytes in vitro constitutively express mRNA for P2Y1R, P2Y2R and P2X7R. CONCLUSION: These results suggest that activation of metabotropic P2YR (P2Y1R and/or P2Y2R) and ionotropic P2X7R could mediate purinergic responses in adult human astrocytes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".