Tafazzin deficiency in mouse mesenchymal stem cells promote reprogramming of activated B lymphocytes toward immunosuppressive phenotypes

Abstract

Barth Syndrome (BTHS) is a rare X‐linked genetic disorder caused by mutation in the TAFAZZIN gene. Tafazzin (Taz) deficiency in BTHS patients results in an increased risk of infections. Mesenchymal stem cells (MSCs) are well known for their immune‐inhibitory function. We examined how Taz‐deficiency in murine MSCs impact their ability to modulate the function of lipopolysaccharide (LPS)‐activated wild type (WT) B lymphocytes. MSCs from tafazzin knockdown (TazKD) mice exhibited a reduction in mitochondrial cardiolipin compared to wild type (WT) MSCs. However, mitochondrial bioenergetics and membrane potential were unaltered. In contrast, TazKD MSCs exhibited increased reactive oxygen species generation and increased glycolysis. The increased glycolysis was associated with an elevated proliferation, phosphatidylinositol‐3‐kinase expression and expression of the immunosuppressive markers indoleamine‐2,3‐dioxygenase, cytotoxic T‐lymphocyte‐associated protein 4, interleukin‐10, and cluster of differentiation 59 compared to controls. Inhibition of glycolysis with 2‐deoxyglucose attenuated the TazKD‐mediated increased expression of cytotoxic T‐lymphocyte‐associated protein 4 and interleukin‐10. When co‐cultured with LPS‐activated WT B cells, TazKD MSCs inhibited B cell proliferation and growth rate and reduced B cell secretion of immunoglobulin M compared to controls. In addition, co‐culture of LPS‐activated WT B cells with TazKD MSCs promoted B cell differentiation toward interleukin‐10 secreting plasma cells and B regulatory cells compared to controls. The results indicate that Taz deficiency in MSCs promote reprogramming of activated B lymphocytes toward immunosuppressive phenotypes.

Tafazzin knockdown in murine mesenchymal stem cells enhances the tafazzin knockdown mediated elevation in interleukin-10 secretion from murine B lymphocytes

“…Increased PI3K expression and activity is associated with enhancement of immunosuppression by MSCs 7 . We previously demonstrated that PI3K protein expression was elevated in MSCs isolated from TazKD mice 5 . MSCs were isolated from bone marrow of WT and TazKD mice and PI3K mRNA expression determined.…”

“…Splenic naïve B lymphocytes from WT and TazKD mice were isolated and cultured as previously described 6 . For co-culture studies with WT or TazKD MSCs, naïve or TazKD B cells were first stimulated by incubation with LPS (10 μg/ml) for 24 h and were then co-cultured with MSCs for 24 h in 24-well plates at a ratio of 1:10 (MSCs:B cells) as previously descibed 5 .…”

“…IL-10 was measured in the supernatant using specific IL-10 antibody (Catalog no. sc-365858) from Santa Cruz Biotechnology (Dallas, TX) as previously described 5 .…”

“…MSCs were isolated from the femurs and tibias of WT or TazKD mice by flushing the bone marrow cells and cultured as previously described 5 . Splenic naïve B lymphocytes from WT and TazKD mice were isolated and cultured as previously described 6 .…”

“…There is limited information on the role of Taz deficiency on other cells of the immune system particularly in the context of cell-to- cell interaction of different immune cell types. We previously demonstrated that lipopolysaccharide (LPS)-activated B lymphocytes from TazKD mice exhibited a reduced ability to secret cytokines, such as interleukin-10 (IL-10), which is known to attract neutrophils to sites of infection 5,6 . In addition, MSCs from TazKD mice impaired the function of LPS-activated WT B lymphocytes.…”