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Cyclic nucleotide levels in resting and mitogen-stimulated spleen cell suspensions from young and old mice
Abstract:
The levels of cyclic adenosine 3', 5'-monophosphate (cAMP) in suspensions of unstimulated spleen cells from tumor-free 30-month old (C57BL/10Sn X C3H/HeDiSn)F1 hybrid mice averaged only 14% of that of 6-month old mice. By contrast, the level of cyclic guanosine 3', 5'-monophosphate (cGMP) in spleen cell suspensions from old mice was about 270% that of young mice. The cAMP/cGMP ratio for the unstimulated (resting) state showed a decline by 30 months to about 5% of its 6-month value. Cyclic nucleotide levels were also measured in cell suspensions from old and young mice at intervals over a two hour period following in vitro stimulation with the plant mitogens phytohemagglutinin, concanavalin-A and pokeweed mitogen. Quantitative and in some instances qualitative differences in responses were noted. These results might conceivably reflect either age-related changes in the splenic lymphoid cell subpopulations or intrinsic cellular alterations or both. It is unlikely that changes of this degree could be wholly explained by population shifts. An imbalance in cyclic nucleotide levels in both resting and stimulated lymphoid cells in older animals might contribute to the immune dysfunction known to occur with normal aging.
Insights
Aging significantly alters immune cell signaling. Older mice exhibit lower cyclic adenosine 3
Area of Science:
- Immunology
- Cellular Biology
- Gerontology
Background:
- Immune dysfunction is a hallmark of aging.
- Cyclic nucleotides like cAMP and cGMP play crucial roles in immune cell function.
- Age-related changes in immune cell signaling pathways are not fully understood.
Purpose of the Study:
- To investigate age-related changes in cyclic nucleotide levels (cAMP and cGMP) in mouse spleen cells.
- To compare the responses of young and old mouse spleen cells to mitogenic stimulation.
Main Methods:
- Measurement of cyclic adenosine 3', 5'-monophosphate (cAMP) and cyclic guanosine 3', 5'-monophosphate (cGMP) levels in spleen cell suspensions from young (6-month) and old (30-month) mice.
- In vitro stimulation of cell suspensions with plant mitogens: phytohemagglutinin, concanavalin-A, and pokeweed mitogen.
- Analysis of cyclic nucleotide levels at baseline and over a two-hour stimulation period.
Main Results:
- Unstimulated spleen cells from old mice showed significantly lower cAMP levels (14% of young mice) and higher cGMP levels (270% of young mice) compared to young mice.
- The cAMP/cGMP ratio in resting cells from old mice was drastically reduced to 5% of the value in young mice.
- Differential quantitative and qualitative responses to mitogenic stimulation were observed between young and old mouse spleen cells.
Conclusions:
- Aging induces a significant imbalance in cyclic nucleotide levels in mouse spleen cells, affecting both resting and stimulated states.
- These age-related alterations in cyclic nucleotide signaling may contribute to the decline in immune function observed in aging.
- The observed changes likely reflect intrinsic cellular alterations rather than solely population shifts in splenic lymphoid cells.