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Nitric oxide-mediated inhibition of caspase-dependent T lymphocyte proliferation
Raja S Mahidhara1, Rosemary A Hoffman, Sulan Huang
1Department of Surgery, University of Pittsburgh School of Medicine, Pennsylvania 15213, USA. mahidharar@msx.upmc.edu
Abstract:
Nitric oxide (NO), a pleiotropic signaling molecule produced at sites of inflammation, is a powerful inhibitor of lymphocyte proliferation. Caspases, central effector proteases in apoptosis, have recently been implicated as critical mediators of T cell activation. We and others have shown that NO can inhibit caspases by S-nitrosylation, which is reversible by the reducing agent dithiothreitol (DTT). The purpose of the present study was to determine whether NO inhibits lymphocyte proliferation by modulating caspase activity. Caspase inhibition with z-VAD-fmk blocked T cell proliferation. NO-dependent inhibition of T cell proliferation was associated with an inhibition of caspase activity and activation, and this effect was reversible by DTT. Previous studies demonstrated inhibition of apoptosis through S-nitrosylation of caspases; the present studies extend this effect to inhibition of caspase-dependent T cell proliferation.
Insights
Nitric oxide (NO) inhibits lymphocyte proliferation by modulating caspase activity, a key factor in T cell activation. This NO-dependent inhibition is reversible by dithiothreitol (DTT), suggesting a role for S-nitrosylation in regulating T cell responses.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Nitric oxide (NO) is a signaling molecule produced during inflammation that inhibits lymphocyte proliferation.
- Caspases are crucial proteases in apoptosis and T cell activation.
- NO inhibits caspases via S-nitrosylation, which is reversible by dithiothreitol (DTT).
Purpose of the Study:
- To investigate if NO inhibits lymphocyte proliferation by modulating caspase activity.
- To determine the role of caspase activity in NO-mediated inhibition of T cell proliferation.
Main Methods:
- Utilized caspase inhibition with z-VAD-fmk to assess its effect on T cell proliferation.
- Measured NO-dependent inhibition of T cell proliferation and its association with caspase activity and activation.
- Assessed the reversibility of NO's effects using dithiothreitol (DTT).
Main Results:
- Caspase inhibition using z-VAD-fmk effectively blocked T cell proliferation.
- NO-dependent inhibition of T cell proliferation correlated with reduced caspase activity and activation.
- The inhibitory effects of NO on T cell proliferation and caspase activity were reversed by DTT.
Conclusions:
- NO inhibits lymphocyte proliferation by modulating caspase activity.
- This study extends the known role of NO in inhibiting apoptosis to include the regulation of caspase-dependent T cell proliferation.
- S-nitrosylation of caspases by NO is a key mechanism in controlling T cell proliferation.