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Immune cells mediate epinephrine secretion from bovine chromaffin cells in vitro
1Department of Physiology, Loyola University Medical Center, Maywood, IL 60153.
Insights
Mononuclear cells release a substance that stimulates epinephrine secretion from adrenal chromaffin cells. This low molecular weight factor, likely a peptide, influences the immune system’s impact on catecholamine release.
Area of Science:
- Immunology
- Neuroendocrinology
- Cell Biology
Background:
- The interplay between the immune system and the nervous system is crucial for maintaining homeostasis.
- Peripheral catecholamine secretion, particularly epinephrine from adrenal chromaffin cells, plays a vital role in the stress response.
- Understanding how immune cells influence neuroendocrine functions is essential for comprehending physiological regulation.
Purpose of the Study:
- To investigate the potential influence of immunological factors on peripheral catecholamine secretion.
- To identify whether mononuclear cells can modulate epinephrine release from chromaffin cells.
- To characterize the nature of the substance mediating this immune-to-endocrine communication.
Main Methods:
- Isolation of chromaffin cells from bovine adrenal medulla and mononuclear cells from bovine spleen or blood.
- In vitro incubation of chromaffin cells with cell-free conditioned media from mononuclear cells.
- Measurement of epinephrine secretion as a percentage of total cellular content.
- Characterization of the active substance using molecular weight filtration, boiling, acid treatment, and dialysis.
- Assessment of the effect of cholinergic (atropine) and nicotinic (hexamethonium) blockade.
Main Results:
- Conditioned media from mononuclear cells significantly stimulated epinephrine secretion (22.8%) compared to control media (1.7%).
- The stimulatory activity was retained after filtration (< 3,000 MW cutoff), indicating a low molecular weight substance.
- Boiling and acid treatment reduced, but did not abolish, the stimulatory effect, suggesting a heat-labile component, possibly peptide-like.
- Dialysis (< 3,000 MW cutoff) significantly reduced the stimulated secretion, confirming the low molecular weight nature of the factor.
- Neither atropine nor hexamethonium blockade affected the conditioned media-induced epinephrine secretion.
Conclusions:
- Mononuclear cells produce and release a low molecular weight substance, likely a peptide.
- This substance actively stimulates epinephrine secretion from adrenal chromaffin cells.
- The findings suggest a novel pathway for immune system modulation of peripheral catecholamine release, independent of direct neural or classical cholinergic pathways.
Abstract:
Potential immunological influences on peripheral catecholamine secretion were investigated by measuring epinephrine secretion from chromaffin cells in vitro in response to cell-free conditioned media from mononuclear cells. Chromaffin cells were isolated from bovine adrenals whereas mononuclear cells were isolated from bovine spleen tissue or whole bovine blood. In secretion experiments epinephrine release and epinephrine remaining in cells was determined such that secretion was expressed as % of total cell content. After 90 minutes exposure to conditioned media, 22.8 +/- 1.1% of content was released compared to 1.7 +/- 0.2% with RPMI media. Secretion after filtration (< 3,000 MW cutoff) was 21.6 +/- 0.9% whereas after boiling and boiling in acid, secretion was 10.2 +/- 0.2 and 4.3 +/- 0.1% respectively. Dialysis (< 3,000 MW cutoff) reduced the 90 min conditioned media-stimulated epinephrine secretion from 22.5 +/- 3.8% to 2.3 +/- 0.3%. Neither atropine nor hexamethonium blockade altered the conditioned media-stimulated epinephrine secretion. These results suggest that mononuclear cells produce a low molecular weight substance--most likely a peptide--that contributes to the stimulation of epinephrine secretion.