Michelle Yu

CD8⁺ memory T (T_M) cells are essential for vaccine-induced protective immunity. While transforming growth factor beta (TGF-β) triggers CD8⁺ T_M cell differentiation, the underlying molecular mechanism(s) has yet to be uncovered. We therefore used a well-established cell culture protocol to prepare TGF-β-triggered CD8⁺ T_M cells derived from chicken ovalbumin (OVA)-specific T cell receptor (TCR) transgenic OTI mice, and systematically characterized them using Western blotting, confocal microscopy, flow cytometry and Seahorse assay analyses. We found that TGF-β/T cells exhibit a T_M cell phenotype (CD62L⁺KLRG1⁻) and display long-term survival upon adoptive transfer into mice. To elucidate the signaling circuitry underpinning the observed transcriptional and metabolic changes required to promote CD8⁺ T_M cell differentiation, we measured the expression of several critical factors and found that TGF-β triggered weak mTORC1 (mTORC1^Weak) signaling. mTORC1^Weak signaling in turn led to an increase in the abundance of key transcriptional (TCF1, FOXO1 and Eomes) and metabolic (AMPK-α1, ATG7, ULK1, SIRT1, OPA1 and LAL) factors and an elevation in mitochondrial mass and reliance on fatty acid oxidation (FAO). Our data thus reveal for the first time that TGF-β regulates CD8⁺ T cell memory by triggering mTORC1^Weak-mediated activation of the transcriptional FOXO1-TCF1-Eomes and metabolic AMPK-ULK1-ATG7 pathways. Given that induction of more qualified CD8⁺ T_M cells is one of the ultimate goals of vaccination, our findings identify additional targets critical to TGF-β-induced T cell memory, which may greatly impact future vaccine development for the treatment of cancer and infectious diseases.

Ondansetron frequently triggers medication safety alerts because of its listing as a ‘known risk’ QT interval‐prolonging medication. We aimed to summarize literature on QT‐prolongation‐related major adverse cardiac events associated with ondansetron. We searched Medline, Embase, International Pharmaceutical Abstracts, and Cochrane Central for randomized controlled trials comparing ondansetron to placebo in adults. Major adverse cardiac events (MACE) included death, nonfatal cardiac arrest, ventricular tachyarrhythmia including torsades de pointes, seizure, or syncope. Random‐effects meta‐analyses were performed with a treatment arm continuity correction for single‐ and double‐zero event studies. We included 170 randomized trials ( n = 23,421, 70.7% female, 48.3% aged >65), 119 trials (70.0%) involving surgical patients, and 77 (45.4%) including electrocardiograms. Mean follow‐up was 10 days (SD: 21.8) (median: 1 day). Risk of bias was high for 11.8% of trials, and low for 28.8%. Only seven MACE (all deaths) were reported. Ondansetron was not associated with increased mortality ( n = 23,421, RR: 1.03, 95% CI: 0.76–1.39, I ² = 0.0%), or arrhythmias. Lack of events precluded prespecified meta‐analyses. Further research on QT‐prolonging medications and their attributed adverse cardiac events and medication alert optimization is needed.

The metabolic poise, or balance, between glycolysis and fatty acid oxidation (FAO) has recently been found to play a critical role in osteogenic differentiation and homeostasis. While simulated microgravity (SMG) is known to impede osteoblast differentiation (OBD) by inhibiting the Wnt/β-catenin pathway, how it affects osteoblast metabolism in this context remains unclear. We previously analyzed the effect of SMG on the differentiation of pre-osteoblast MC3T3-E1 cells and found that it reduced focal adhesion kinase (FAK) activity. This, in turn, downregulated Wnt/β-catenin and two of its downstream targets critical for OBD bone morphogenic protein-2 (BMP2) and type-1 collagen (COL1) formation, leading to a reduction in alkaline phosphatase (ALP) activity and cell matrix mineralization. In this study, we further analyzed how SMG-induced alterations in energy metabolism contribute to the inhibition of OBD in MC3T3-E1 cells. Consistent with our earlier findings, we demonstrated that SMG inhibits OBD by downregulating the collective activity of FAK and the Wnt/β-catenin-BMP2-COL1 transcriptional pathway. Interestingly, we observed that SMG also reduces the abundance of sirtuin-1 (SIRT1), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) and carnitine palmitoyl transferase-1α (CPT1A), which are all key metabolic factors regulating mitochondrial number and FAO capacity. Accordingly, we found that the mitochondrial content and FAO potential of MC3T3-E1 cells were lower upon exposure to SMG but were both rescued upon administration of the FAK activator cytotoxic necrotizing factor-1 (CNF1), thereby allowing cells to overcome SMG-induced inhibition of OBD. Taken together, our study indicates that the metabolic regulator SIRT1 may be a new target for reversing SMG-induced bone loss.