Retinoblastoma protein induction by HIV viremia or CCR5 in monocytes exposed to HIV-1 mediates protection from activation-induced apoptosis: ex vivo and in vitro study

J Leukoc Biol. 2012 Aug;92(2):397-405. doi: 10.1189/jlb.1111552. Epub 2012 Jun 13.

Abstract

We have previously described an antiapoptotic steady-state gene expression profile in circulating human monocytes from asymptomatic viremic HIV(+) donors, but the mechanism associated with this apoptosis resistance remains to be fully elucidated. Here, we show that Rb1 activation is a dominant feature of apoptosis resistance in monocytes exposed to HIV-1 in vivo (as measured ex vivo) and in vitro. Monocytes from asymptomatic viremic HIV(+) individuals show a positive correlation between levels of hypophosphorylated (active) Rb1 and VL in conjunction with increases in other p53-inducible proteins associated with antiapoptosis regulation, such as p21 and PAI-1 (SERPINE1), when compared with circulating monocytes from uninfected donors. Monocytes exposed in vitro to HIV-1 R5 isolates but not X4 isolates showed lower caspase-3 activation after apoptosis induction, indicating a role for the CCR5 signaling pathway. Moreover, monocytes exposed to R5 HIV-1 or MIP-1 β induced Rb1 and p21 expression and an accumulation of autophagy markers, LC3 and Beclin. The inhibition of Rb1 activity in HIV-1 R5 viral-exposed monocytes using siRNA led to increased apoptosis sensitivity, thereby confirming a central role for Rb1 in the antiapoptotic phenotype. Our data identify Rb1 induction in chronic asymptomatic HIV-1 infection as a mediator of apoptosis resistance in monocytes in association with protective autophagy and contributing to monocyte survival during immune activation and/or HIV-1 viremia.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / immunology*
  • HIV Infections / immunology*
  • HIV-1 / immunology*
  • Humans
  • Monocytes / cytology
  • Monocytes / immunology
  • Monocytes / virology*
  • Receptors, CCR5 / genetics
  • Receptors, CCR5 / metabolism
  • Receptors, CCR5 / physiology*
  • Retinoblastoma Protein / biosynthesis*
  • Retinoblastoma Protein / genetics*
  • Retinoblastoma Protein / physiology
  • Signal Transduction / immunology
  • Transcriptional Activation / immunology
  • Viremia / immunology
  • Virus Inactivation

Substances

  • Receptors, CCR5
  • Retinoblastoma Protein