Forkhead box O3 (FOXO3) transcription factor mediates apoptosis in BCG-infected macrophages

Abstract

Enhanced apoptosis of BCG-infected macrophages has been shown to induce stronger dendritic cell-mediated cross-priming of T cells, leading to higher protection against tuberculosis (TB). Uncovering host effectors underlying BCG-induced apoptosis may then prove useful to improve BCG efficacy through priming macrophage apoptosis. Her we report that BCG-mediated apoptosis of human macrophages relies on FOXO3 transcription factor activation. BCG induced a significant apoptosis of THP1 (TDMs) and human monocytes (MDMs)-derived macrophages when a high moi was used, as shown by annexin V/7-AAD staining. BCG-induced apoptosis was associated with dephosphorylation of the prosurvival activated threonine kinase (Akt) and its target FOXO3. Cell fractionation and immunofluorescence microscopy showed translocation of FOXO3 to the nucleus in BCG-infected cells, concomitantly with an increase of FOXO3 transcriptional activity. Moreover, FOXO3 expression knock-down by small interfering RNA (siRNA) partially inhibited the BCG-induced apoptosis. Finally, real-time quantitative PCR (qRT-PCR) analysis of the expression profile of BCG-infected macrophages showed an upregulation of two pro-apoptotic targets of FOXO3, NOXA and p53 upregulated modulator of apoptosis (PUMA). Our results thus indicate that FOXO3 plays an important role in BCG-induced apoptosis of human macrophages and may represent a potential target to improve vaccine efficacy through enhanced apoptosis-mediated cross-priming of T cells.

Inhibition of TLR8 mediated signaling promotes BCG induced apoptosis in THP-1 cells

“…In a siRNA screen experiment looking for host M A N U S C R I P T A C C E P T E D independent, which was consistent with the previous report [18]. However, 215 the increased apoptosis due to TLR8 knockdown was caspase dependent.…”

FOXO3 rs12212067: T > G Association with Active Tuberculosis in Han Chinese Population

“…FOXO transcription factors respond to growth factors, oxidative stress, inflammation, and nutritional abundance-physiological conditions that influence the magnitude and effectiveness of an immune response [22]. FOXO3 has been reported to contribute to the pathogenesis of several immuneassociated disorders, including TB [23]; furthermore, the genetic variation at rs12212067 in FOXO3 is also associated with prognosis in malaria [18]. However, the genetic association of FOXO3 variations and TB is poorly understood.…”

Two distinct conformational states of Mycobacterium tuberculosis virulent factor early secreted antigenic target 6 kDa are behind the discrepancy around its biological functions

“…BCG Pasteur strain 1173P2 (6 × 10 8 viable units·mL −1 per vial) was obtained from the serum and vaccine production department at Pasteur Institute of Tunis (Fresh Immune BCG catalog number 30106). A single cell suspension of mycobacteria was prepared as described previously . Bacterial viability/enumeration was assessed by CFU on Middlebrook 7H10 agar (BD Pharmingen, San Diego, CA, USA) supplemented with oleic acid, albumin, dextrose and catalase (BD Pharmingen).…”