S-adenosylmethionine (SAM) is the main cellular methyl donor and a core product of one-carbon metabolism. Its balance with S-adenosylhomocysteine (SAH) defines methylation potential and shapes epigenetic and epitranscriptomic outputs. RNA N6-methyladenosine (m6A) directly depends on SAM and is controlled by a writer-reader-eraser system. This review summarizes how altered SAM supply, SAH accumulation, and shifts in the SAM/SAH ratio can reprogram m6A landscapes. These changes can occur in cancer, metabolic disease, inflammation, and neurodegeneration. We integrate metabolic control of SAM generation and consumption with regulation of METTL3/METTL14, WTAP and related cofactors, and the erasers FTO and ALKBH5. We also assess plant-derived bioactive compounds proposed to act on this coupling. Most phytochemicals do not behave as potent, selective m6A enzyme inhibitors. They more often act upstream by reshaping one-carbon metabolism, redox state, and protein expression. This profile contrasts with canonical synthetic inhibitors that block a single node with higher affinity and more predictable pharmacodynamics. Together, the evidence supports the SAM-m6A axis as a practical framework to connect nutrient state with RNA fate decisions. It also highlights key gaps for translation, including target engagement, dose-exposure alignment, and causal validation of m6A-dependent phenotypes.

Recurrence of high-risk advanced retinoblastoma (RB) is still a major obstacle even after enucleation due to resistance to adjuvant chemotherapy, especially in China. To identify any germline alterations or candidate genes associated with RB prognosis, we obtained whole-exome sequencing (WES) and reduced-representation bisulfite sequencing (RRBS) profiles by using patient peripheral blood samples, followed by clinical validation and functional characterization. For follow-up studies, we selected 17 candidate genes from the WES and RRBS analyses. Among them, MBD4, which carries a germline loss-of-function mutation (rs140693), was identified for further clinical replication. MBD4 downregulation significantly impaired carboplatin or etoposide efficacy in vitro and in vivo, respectively. There were marked decreases in the expression of 5 related genes plus increased DNA methylation in their promoters in Y79 (MBD4-/-) cells, along with even more significant effects after carboplatin treatment. MBD4 affected the transcription and expression of its downstream genes, such as FADD and P21, via MBDCap-PCR, ChIPqPCR, and reporter gene assays. Moreover, the germline mutation was responsible for MBD4 instability with attenuated binding to USP7, thereby leading to impaired drug sensitivity. It was confirmed by the reinstated susceptibility of Y79 (MBD4-/-) cells after MBD4-WT was restored. In the present study, our findings indicate that depletion or mutation of MBD4 interferes with the activation of the cell cycle and apoptosis via epigenetic regulation, thereby reducing drug susceptibility. It provides new insights into the role in RB chemoresistance of MBD4 as an epigenetic regulator, which might fuel the development of new RB-targeted strategies.

G protein-coupled receptors (GPCRs) remain among the most important drug targets. To characterize their ligands' activity, a range of in vitro assays is available, all with their inherent advantages and limitations. In the Gαq signaling pathway, the interaction between Gαq and phospholipase C (PLC-)β is a receptor-proximal event, and its monitoring does not require modification of the GPCR. With this in mind, we set out to develop a luminescence-based assay gauging this interaction. The resulting assay format encompassed functional complementation of a split nanoluciferase following the interaction of SmBiT, N-terminally fused to PLC-β, with LgBiT, intramolecularly integrated within Gαq. When applied to assess activation of the Gαq-coupled serotonin 2 A receptor (5-HT2AR), an excellent assay performance was demonstrated, as evidenced by an auspicious Z'-factor of 0.75 and by confirming the specificity for both the GPCR and the Gαq signaling pathway. The optimized Gαq-PLC-β assay was successfully applied on a diverse panel of 5-HT2AR ligands and the resulting output was compared with that of a more upstream miniGαq recruitment assay, and more downstream IP1 accumulation and Ca2+ mobilization assays. Overall, the Gαq-PLC-β assay yielded efficacy, potency and relative activity data that correlated very well with those obtained with the IP1 accumulation and miniGαq recruitment assays, although with the former two assays consistently higher potencies and a smaller range of efficacies were observed. Comparison with the Ca2+ mobilization assay did not yield such good correlation, presumably because of kinetic implications. Last, the Gαq-PLC-β interaction assay allowed to detect signals emerging from endogenously expressed GPCRs, indicative of its broad applicability.

With the global population growing and aging, along with increasing environmental, metabolic, and lifestyle-related risk factors, the worldwide incidence of stroke, Alzheimer's disease (AD) and other dementias, meningitis, and other neurological disorders-along with associated mortality-has risen significantly. Proanthocyanidins (PCs), which are oligomers and polymers of flavan-3-ols, are widely distributed across the plant kingdom, including in grape seeds, cinnamon, apples, cranberries, lotus seeds, and pine bark. They represent the second most abundant class of polyphenols in nature, after lignin. A substantial body of preclinical evidence indicates that PCs exert significant neuroprotective effects through multiple mechanisms. This review provides a systematic overview of the sources, structural characteristics, and bioavailability of PCs, with a focus on their pharmacological mechanisms in nervous system disease. Specifically, it examines their roles in regulating oxidative stress, neuroinflammation, protein homeostasis, apoptosis, autophagy, and key signaling pathways, including Nrf2/HO-1, CREB/BDNF, PI3K/Akt, MAPK, and NF-κB. Furthermore, this review systematically summarized the distinct structural forms of PCs, including monomers, dimers, trimers, and polymers, and explores their structure-activity relationships (SARs) in modulating the gut-brain axis. Additionally, recent advances in PCS-based nano-delivery systems and clinical studies related to neurological disorders are summarized. Growing evidence indicates that microbial metabolism in the gut serves as a key mechanism underlying their neuroprotective effects. Finally, the potential applications of PCs as promising dietary supplements or therapeutic agents for the prevention and treatment of nervous system diseases are discussed, along with existing challenges and future perspectives.