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Dexamethasone induces apoptosis in mouse natural killer cells and cytotoxic T lymphocytes
G Migliorati1, I Nicoletti, F D'Adamio
1Institute of Farmacologia Medica, Perugia University Medical School, Italy.
Abstract:
Glucocorticoid hormones (GCH) induce apoptotic cell death in immature thymocytes through an active mechanism, characterized by extensive DNA fragmentation into oligonucleosomal subunits. This requires macromolecular synthesis and is inhibited by protein kinase C (PKC) inhibitors, interleukin-4 (IL-4) and heat shock (hs). We performed experiments to analyse the possible effect of GCH on more differentiated lymphocytes, i.e. mouse natural killer (NK) cells and CD8+ alloreactive cytotoxic T lymphocytes (CTL). The results show that dexamethasone (DEX) induces DNA fragmentation and cell death in NK cells and CTL in vitro. In both NK cells and CTL, DEX-induced apoptosis is inhibited by IL-2 and IL-4 but, unlike that induced in thymocytes, is augmented by mRNA and protein synthesis inhibitors, PKC inhibitors and HS.
Insights
Glucocorticoid hormones induce apoptosis in mature lymphocytes like NK cells and CTLs. Unlike thymocytes, this process is enhanced by synthesis inhibitors and protein kinase C inhibitors.
Area of Science:
- Immunology
- Cell Biology
- Endocrinology
Background:
- Glucocorticoid hormones (GCH) are known to induce apoptosis in immature thymocytes via an active mechanism involving DNA fragmentation.
- This process in thymocytes is inhibited by protein kinase C (PKC) inhibitors, interleukin-4 (IL-4), and heat shock (HS), and requires macromolecular synthesis.
Purpose of the Study:
- To investigate the effects of GCH on more differentiated lymphocytes, specifically mouse natural killer (NK) cells and CD8+ alloreactive cytotoxic T lymphocytes (CTL).
- To compare the mechanisms of GCH-induced apoptosis in differentiated lymphocytes with those in immature thymocytes.
Main Methods:
- In vitro experiments exposing NK cells and CTLs to dexamethasone (DEX), a synthetic GCH.
- Analysis of DNA fragmentation and cell death as indicators of apoptosis.
- Assessment of the effects of various inhibitors (mRNA and protein synthesis inhibitors, PKC inhibitors) and conditions (HS, IL-2, IL-4) on DEX-induced apoptosis.
Main Results:
- Dexamethasone (DEX) induces DNA fragmentation and cell death in both NK cells and CTLs in vitro.
- Apoptosis in NK cells and CTLs is inhibited by IL-2 and IL-4.
- Conversely, unlike in thymocytes, DEX-induced apoptosis in NK cells and CTLs is augmented by mRNA and protein synthesis inhibitors, PKC inhibitors, and heat shock (HS).
Conclusions:
- Glucocorticoid hormones induce apoptosis in differentiated lymphocytes (NK cells and CTLs) through a distinct mechanism compared to immature thymocytes.
- The sensitivity of GCH-induced apoptosis to synthesis inhibitors and PKC inhibitors differs between immature thymocytes and mature lymphocytes, suggesting differential regulatory pathways.