Apoptosis‐related mitochondrial dysfunction defines human monocyte‐derived dendritic cells with impaired immuno‐stimulatory capacities

Abstract

The death of dendritic cells (DCs) can potentially influence immune responses by affecting the duration of DC stimulation of lymphocytes. Here, we report that cultured mature monocyte-derived DCs manifest early mitochondrial damage (i.e. within 24 hrs), characterized by mitochondrial membrane potential (ψΔm) disruption and mitochondrial release of pro-apoptotic factors, followed by reactive oxygen species (ROS) production and activation of caspases. Afterwards, DCs with mitochondrial alterations are condemned to undergo apoptosis and necrosis. Macroarray analysis results (validated by real time quantitative-PCR (QRT-PCR) and immunoblotting), showed up-regulation of the pro-apoptotic member of the Bcl-2 family, Bim, while expression of several anti-apoptotic molecules was down-regulated. Importantly, pre-apoptotic DCs (characterized by a low Δψm) showed a modified phenotype, with down-regulation.of HLA-DR and of the co-stimulatory molecules CD80 and CD86. Moreover, sorted viable low ψΔm DCs were unable to activate allogeneic T cells, indicating that pre-apoptotic DCs have already lost some of their immuno-stimulatory capabilities long before any detectable signs of death occur. Perturbations to mitochondrial respiration with rotenone identified the same modifications to DC immune functions. These data indicate a strong requirement for mitochondrial integrity for the immuno-stimulatory capacities of DC. Determining ΔΨm could be a useful parameter to select ‘fully’ functional DCs for anti-tumour vaccines.

Commitment to glycolysis sustains survival of NO-producing inflammatory dendritic cells

“…Whereas resting DCs showed characteristic changes in OCR in response to inhibition of the mitochondrial ATP-synthase by oligomycin, uncoupling of OXPHOS from ATP synthesis by FCCP and inhibition of the electron transport chain (ETC) by antimycin-A/rotenone (explained in supplemental Figure 1, available on the Blood Web site; see the Supplemental Materials link at the top of the online article), DCs that had been activated for 24 hours by LPS were entirely nonresponsive to these drugs ( Figure 1B). Consistent with these observations, O 2 Ϫ production ( Figure 1C) and mitochondrial membrane potential (⌬⌿ m ; Figure 1D), indicators of ETC use, 14 were significantly reduced in these cells. This phenomenon was not specific to TLR4-activated DCs, because other TLR agonists (with the exception of the TLR1/2 agonist Pam3cys) induced similar declines in mitochondrial respiration in these DCs (supplemental Figure 2A).…”

Profound and persistent decrease of circulating dendritic cells is associated with ICU-acquired infection in patients with septic shock

“…A direct downregulation of HLA-DR expression at the surface of DCs or the differentiation of monocytes with sepsis-induced loss of HLA-DR expression [15,21] into a subpopulation of circulating DCs with altered maturation could explain this finding. A decrease of membrane HLA-DR expression on DCs may also indicate DC apoptosis [22]. Finally, in the small cohort reported by Poehlmann et al [20], DC counts failed to return to normal values in the 12 patients that were still alive at day 28, but the data provided do not permit any conclusion to be drawn regarding the link with ICU-acquired infection or patient outcome.…”

Ammonia Drives Dendritic Cells into Dysfunction

“…Rotenone has been shown to prevent the increase of mitochondrial number and inhibit DC differentiation (27). Furthermore, mitochondrial membrane potential-disrupted DCs were unable to activate allogenic T cells (28). These findings clarified the importance of mitochondria in DCs.…”