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IL-7 inhibits dexamethasone-induced apoptosis via Akt/PKB in mature, peripheral T cells

Hadassah Sade1, Apurva Sarin

  • 1National Centre for Biological Sciences, UAS-GKVK Campus, Bangalore, India.

European Journal of Immunology
|April 3, 2003
PubMed

Insights

Interleukin-7 (IL-7) prevents T cell death induced by dexamethasone by activating the Akt pathway, which regulates the expression of apoptosis-inhibiting proteins like IAP-2 and Bcl-x(L). This research clarifies IL-7

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • Dexamethasone induces apoptosis in mature T cells, a process involving caspase activation and mitochondrial dysfunction.
  • Interleukin-7 (IL-7) is known to promote T cell survival, but its precise mechanism in preventing dexamethasone-induced apoptosis requires elucidation.

Purpose of the Study:

  • To investigate the molecular mechanisms by which IL-7 inhibits dexamethasone-induced apoptosis in mature T cells.
  • To identify the specific signaling pathways and proteins involved in IL-7's protective effect.

Main Methods:

  • Isolation of CD3(+) mature T cells from adult mouse spleens.
  • Treatment with dexamethasone and IL-7, with or without caspase inhibitors, PI3K inhibitors, or constitutively active Akt.
  • Analysis of apoptosis markers (nuclear fragmentation, mitochondrial potential, membrane integrity), caspase processing, protein levels (Bcl-x(L), IAP-2), and signaling pathway activation (Akt, Bad phosphorylation).

Main Results:

  • IL-7 inhibited dexamethasone-induced apoptosis, caspase processing, and Bad dephosphorylation.
  • IL-7 blocked the downregulation of anti-apoptotic proteins Bcl-x(L) and inhibitor of apoptosis protein-2 (IAP-2).
  • The protective effect of IL-7 was largely dependent on phosphatidylinositol-3 kinase (PI3K)/Akt signaling for IAP-2 regulation but not for Bcl-x(L) regulation.

Conclusions:

  • IL-7 inhibits dexamethasone-induced T cell apoptosis by activating Akt via PI3K-dependent signaling, leading to increased IAP-2 expression.
  • IL-7 also regulates Bcl-x(L) expression through a PI3K-independent pathway, contributing to T cell survival.
  • These findings highlight distinct signaling pathways modulated by IL-7 for the differential regulation of anti-apoptotic proteins in mature T cells.

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