Mitochondrial metabolism supports resistance to IDH mutant inhibitors in acute myeloid leukemia

Mutations in IDH induce epigenetic and transcriptional reprogramming, differentiation bias, and susceptibility to mitochondrial inhibitors in cancer cells. Here, we first show that cell lines, PDXs, and patients with acute myeloid leukemia (AML) harboring an IDH mutation displayed an enhanced mitochondrial oxidative metabolism. Along with an increase in TCA cycle intermediates, this AML-specific metabolic behavior mechanistically occurred through the increase in electron transport chain complex I activity, mitochondrial respiration, and methylation-driven CEBPα-induced fatty acid β-oxidation of IDH1 mutant cells. While IDH1 mutant inhibitor reduced 2-HG oncometabolite and CEBPα methylation, it failed to reverse FAO and OxPHOS. These mitochondrial activities were maintained through the inhibition of Akt and enhanced activation of peroxisome proliferator-activated receptor-γ coactivator-1 PGC1α upon IDH1 mutant inhibitor. Accordingly, OxPHOS inhibitors improved anti-AML efficacy of IDH mutant inhibitors in vivo. This work provides a scientific rationale for combinatory mitochondrial-targeted therapies to treat IDH mutant AML patients, especially those unresponsive to or relapsing from IDH mutant inhibitors.

Role of macrophages during skeletal muscle regeneration and hypertrophy-Implications for immunomodulatory strategies

Skeletal muscle is a plastic tissue that regenerates ad integrum after injury and adapts to raise mechanical loading/contractile activity by increasing its mass and/or myofiber size, a phenomenon commonly refers to as skeletal muscle hypertrophy. Both muscle regeneration and hypertrophy rely on the interactions between muscle stem cells and their neighborhood, which include inflammatory cells, and particularly macrophages. This review first summarizes the role of macrophages in muscle regeneration in various animal models of injury and in response to exercise-induced muscle damage in humans. Then, the potential contribution of macrophages to skeletal muscle hypertrophy is discussed on the basis of both animal and human experiments. We also present a brief comparative analysis of the role of macrophages during muscle regeneration versus hypertrophy. Finally, we summarize the current knowledge on the impact of different immunomodulatory strategies, such as heat therapy, cooling, massage, nonsteroidal anti-inflammatory drugs and resolvins, on skeletal muscle regeneration and their potential impact on muscle hypertrophy.

Neuromuscular electrical stimulation training induces myonuclear accretion and hypertrophy in mice without overt signs of muscle damage and regeneration

BACKGROUND

Skeletal muscle is a plastic tissue that adapts to increased mechanical loading/contractile activity through fusion of muscle stem cells (MuSCs) with myofibers, a physiological process referred to as myonuclear accretion. However, it is still unclear whether myonuclear accretion is driven by increased mechanical loading per se, or occurs, at least in part, in response to muscle injury/regeneration. Here, we developed a non-damaging protocol to evaluate contractile activity-induced myonuclear accretion/hypertrophy in physiological conditions.

METHODS

Contractile activity was generated by applying repeated electrical stimuli over the mouse plantar flexor muscles. This method is commonly referred to as NeuroMuscular Electrical Simulation (NMES) in Human. Each NMES training session consisted of 80 isometric contractions delivered at ∼15% of maximal tetanic force to avoid muscle damage. C57BL/6J male mice were submitted to either a short (i.e., 6 sessions) or long (i.e., 12 sessions) individualized NMES training program while unstimulated mice were used as controls. Histological investigations were performed to assess the impact of NMES on MuSC number and status, myonuclei content and muscle tissue integrity, typology and size.

RESULTS

NMES led to a robust proliferation of MuSCs and myonuclear accretion in the absence of overt signs of muscle damage/regeneration. NMES-induced myonuclear accretion was specific to type IIB myofibers and was an early event preceding muscle hypertrophy inasmuch as a mild increase in myofiber cross-sectional area was only observed in response to the long-term NMES training protocol.

CONCLUSION

We conclude that NMES-induced myonuclear accretion and muscle hypertrophy are driven by a mild increase in mechanical loading in the absence of overt signs of muscle injury.

Understanding Cardiovascular Events With JAK Inhibitors: Tofacitinib Reduces Synovial and Vascular Inflammation but not the Prothrombotic Effects of Inflammatory Cytokines on Endothelium

OBJECTIVE

Inflammation drives cardiovascular disease in rheumatoid arthritis (RA). Treatment with tofacitinib, a JAK1/JAK3 inhibitor, is associated with increased cardiovascular events in patients with RA. Here, we determined its effects on cytokine production during interactions between immune cells at the synovial and vascular levels and its impact on endothelial activation and coagulation during inflammation.

METHODS

Activated human peripheral blood mononuclear cells (PBMCs) were cocultured with RA synoviocytes or endothelial cells (ECs) mimicking the cellular interactions in synovium and vessels responsible for cytokine production. A dose-response of tofacitinib was tested on interferon γ, interleukin (IL) 17A, IL-10, IL-6, and IL-1β, and cytokine production was measured by enzyme-linked immunosorbent assay at 48 hours. Endothelial activation was induced with IL-17A and tumor necrosis factor (TNF) or on contact with PBMCs. Shortly after tofacitinib treatment, the expression of EC activation markers, specifically IL-6, IL-8, vascular cell adhesion molecule 1 (VCAM-1), and E-selectin, and of coagulation, including tissue factor and thrombomodulin, was assessed by real-time polymerase chain reaction.

RESULTS

Tofacitinib differentially inhibited production of IFNɣ, IL-17A, and IL-10 from PBMC cocultures with RA synoviocytes or ECs (all P < 0.001). In cocultures with ECs, tofacitinib reduced further IL-6 and IL-8 production (both P < 0.001). In ECs activated by TNF/IL-17A or indirectly via contact with activated PBMCs, tofacitinib decreased IL-6 upregulation but not that of IL-8, E-selectin, or tissue factor. Thrombomodulin was significantly decreased. VCAM-1 was greatly induced with a higher dose of tofacitinib in ECs incubated directly with added inflammatory cytokines (P < 0.05) or released by interaction with activated PBMCs (P < 0.001).

CONCLUSION

Tofacitinib inhibits synovium and vascular inflammation but fails to prevent the prothrombotic effects of inflammatory cytokines on ECs.