As an important strategy in antiviral drug development, nucleoside analogs (NAs) have attracted considerable attention due to their unique mechanisms of action and favorable safety profile. This review systematically summarizes recent advances in the mechanisms of action of NAs, focusing on the following four aspects: (1) Targeting viral polymerases, inhibiting viral replication through mechanisms such as non-absolute termination, delayed chain termination and induction of viral RNA mutations in addition to classical chain termination, which has been newly discovered; (2) Regulating RNA methylation modifications—for instance, competitively inhibiting methyltransferases, which significantly reduces viral replication efficiency; (3) Depleting nucleotide pools—by affecting host cell purine nucleotide synthesis pathways, thereby indirectly inhibiting viral replication; and (4) Immunomodulatory functions—including activation of the STING pathway to promote interferon production. Furthermore, this review systematically discusses the breakthrough progress in prodrug technologies for addressing key clinical challenges such as drug resistance and off-target toxicity of NAs. These advances provide crucial technical support for the clinical translation of NAs. These advances provide key technical support for the clinical translation of NAs. This review clarifies the multi-target action rules of NAs and provides a theoretical framework for the design of next-generation broad-spectrum antiviral agents.

Objective: To investigate the molecular mechanisms and pathways of action of total flavonoids of Dracocephalum moldavica L.(TFDM) in treating vascular cognitive impairment(VCI) based on network pharmacology and in vivo animal experiments. Methods : The swiss target prediction database, literature, and PubChem were used to screen the active components and action targets of TFDM. The online mendelian inheritance in man(OMIM) and GeneCards databases were utilized to screen for possible VCI targets. Venny software was used to obtain the intersection target of TFDM and VCI. The search tool for recurring instances of neighbouring genes(String) database and Cytoscape software was used to construct the PPI network. The database for annotation, visualization and integrated discovery(DAVID) database was utilized to screen for the kyoto encyclopedia of genes and genomes(KEGG) pathway and gene ontology(GO) enrichment analyses to explore the molecular mechanism and signaling pathway of TFDM for VCI. 24 rats were divided into Sham, Model, Donepezil, and TFDM groups. Except for the Sham group, the VCI model was created using modified bilateral common carotid artery ligation. After continuous gavage for 21 days, the Morris water maze test was used to evaluate the spatial learning and memory ability of rats. Hematoxy-lineosin(HE) staining was used to observe the pathological changes in the hippocampal CA1 and cortex region of the animals and immunohistochemistry detection of zonula occludens-1(ZO-1) content in the brains of the rats. Western blot was used to detect nuclear factor kappa-B p65(NF-κB p65) and tumor necrosis factor-α(TNF-α) in rat brains. Results : A total of 39 active ingredients of TFDM were screened, 209 corresponding targets, 10 417 gene targets of VCI, and 193 intersecting targets. According to the results of the GO enrichment of function analysis, TFDM could improve the response of reactive oxygen species and metabolic processes of reactive oxygen species, etc. KEGG pathway enrichment analysis suggested that TFDM might regulate TNF, IL-17 signing pathway, etc. The results of animal experiments showed that TFDM improved learning and memory while reduced pathological damage in the brains of VCI rats. In addition, TFDM upregulated the positive expression of ZO-1 and downregulated the protein levels of TNF-α and NF-κB p65(P<0.05). Conclusion TFDM can improve the cognitive function of VCI through multi-components and multi-targets, and its key mechanism may be related to inhibiting TNF-α/NF-κB p65 signaling pathway,reducing neuroinflammation,and improvement of blood-brain barrier permeability.