Objective To investigate the effects of meropenem and amikacin on gut microbiota diversity and composition in a neonatal rat model of necrotizing enterocolitis(NEC).Methods Neonatal SD rats(1～2 d,weighing 5～10 g,both sexes)were subjected to establish a NEC model through artificial formula feeding,hypoxic-cold stress,and lipopolysaccharide(LPS)gavage.The rats were randomly divided into normal control group(Group C,n=12),NEC group(Group N,n=20),meropenem intervention group(Group M,n=20),and amikacin intervention group(Group A,n=20).Following modeling,Group M and Group A received intraperitoneal injections of meropenem(125 mg/kg)or amikacin(468 mg/kg),twice daily for 3 consecutive days.Groups C and N were administered an equal volume of normal saline.At the end of the intervention,colonic contents or fecal samples were collected.The gut microbiota structure was analyzed using 16S rDNA high-throughput sequencing.Bioinformatics analysis was performed using the QIIME2 platform.Alpha diversity was evaluated using Chao1,Shannon,and Simpson indices.Beta diversity was assessed based on Bray-Curtis distance through principal coordinate analysis(PCoA)and non-metric multidimensional scaling(NMDS).Venn and UpSet plots were generated to visualize the composition and overlap of operational taxonomic units(OTUs).Linear discriminant analysis effect size(LEfSe)was applied to identify differentially abundant taxa across groups.Results High-throughput 16S rDNA sequencing showed that the N group had significantly lower 3 indices of α diversity than the C group(P<0.01),that is,a Chao1 index from 230 to 40,a Shannon index from 1.65 to 0.85,and a Simpson index from 0.65 to 0.42.After antibiotic intervention,both the M group and A group obtained obvious increases in the Chao1 index than the N group(P<0.001),with a greater increase observed in the M group than in the A group(P<0.05).However,neither antibiotic group exhibited notable improvements in the Shannon index or Simpson index compared with the N group(P>0.05).Venn and UpSet analyses revealed that the M group had the highest number of unique OTUs(283),while the A group shared the most OTUs(63)with the C group.PCoA and NMDS analyses indicated that the microbial structure of the A group was closer to that of the C group,with better clustering.Taxonomic composition and LEfSe analysis demonstrated that the N group was enriched with potentially pathogenic taxa such as Escherichia coli B2 and Klebsiella under the phylum Proteobacteria,while beneficial bacteria including Lactobacillaceae and Bifidobacteriaceae(phylum Firmicutes)were significantly reduced,indicating severe dysbiosis.In contrast,the A group exhibited a significant increase in beneficial bacteria and a structural tendency toward ecological recovery.The M group,however,was enriched with various conditionally pathogenic and environmentally associated genera,displaying a microbial configuration notably deviating from a healthy state.Conclusion Meropenem and amikacin exhibit differential regulatory effects on the intestinal microbiota in the context of NEC.Amikacin demonstrates superior efficacy in restoring microbial stability and levels of beneficial bacteria,whereas meropenem,although effective for early infection control,warrants caution due to its potential long-term impact on the gut microbiome.

Objective:To investigate the role of microRNA-25-5p (miR-25-5p) in melanogenesis, and to explore its underlying mechanisms.Methods:Target genes of miR-25-5p were predicted using the TargetScan database. The interaction between miR-25-5p and the 3' untranslated region (3' UTR) of the RAB11B gene (a member of RAS oncogene family) was validated through a dual-luciferase reporter assay. Post-inflammatory hyperpigmentation (PIH) models were established in female C57BL/6J mice (6 - 8 weeks old) and female brown guinea pigs (4 - 6 weeks old) through daily broadband ultraviolet B (UVB) irradiation on the dorsal skin of the mouse ear or shaved dorsal skin of guinea pigs, while untreated mice and untreated dorsal skin areas of guinea pigs served as control groups. During modeling, these experimental animals received intradermal injections of a miR-25-5p agomir or a miR control agomir. Changes in skin pigmentation were observed, and skin tissue samples were harvested for further analysis after modeling. Melanin content in skin tissues was evaluated using Masson-Fontana staining. Expression of RAB11B and tyrosinase (TYR) in skin tissues was determined using immunohistochemical staining and quantitative real-time PCR (qPCR). Primary human melanocytes were isolated from discarded normal foreskin tissues of healthy males after circumcision. Both primary human melanocytes and human MNT1 melanoma cells were transfected with miR-25-5p mimics or miR control mimics. Relative expression levels of miR-25-5p and RAB11B mRNA were quantified by qPCR using the 2 -ΔΔCt calculation method. In MNT1 cells, miR-25-5p and RAB11B were co-overexpressed to assess their effect on the mRNA expression of RAB11B and TYR. Statistical analysis was conducted using t test or one-way analysis of variance followed by Tukey's post hoc test for multiple comparisons. Results:The bioinformatic prediction and dual-luciferase reporter assay confirmed a binding site for miR-25-5p in the 3′ UTR of the RAB11B gene. In both animal models, the treatment with the miR-25-5p agomir significantly reduced local skin pigmentation compared to the control groups; Masson-Fontana staining showed a marked decrease in the density of melanin granules in the epidermis and dermis in the miR-25-5p agomir groups compared with the miR control agomir groups (mice: 0.050 ± 0.005 vs. 0.087 ± 0.008; guinea pigs: 0.067 ± 0.015 vs. 0.110 ± 0.013; both P < 0.05). Immunohistochemical staining revealed significantly lower expression of RAB11B in mouse skin tissues in the miR-25-5p agomir group than in those in the miR control agomir group (both P < 0.05). qPCR revealed significantly lower mRNA expression of RAB11B and TYR in skin tissues of guinea pigs in the miR-25-5p agomir group than in those in the miR control agomir group (both P < 0.05). Similarly, RAB11B mRNA expression significantly decreased in the miR-25-5p mimics group compared with the miR control mimics group in primary human melanocytes and MNT1 cells (both P < 0.05). In human MNT1 melanoma cells, miR-25-5p overexpression could suppress TYR mRNA expression, whereas co-overexpression of miR-25-5p and RAB11B could reverse this suppression. Conclusion:Overexpression of miR-25-5p could alleviate UVB-induced post-inflammatory hyperpigmentation and inhibit melanogenesis, likely by targeted suppression of RAB11B expression.

Objective:To investigate the role of microRNA-25-5p (miR-25-5p) in melanogenesis, and to explore its underlying mechanisms.Methods:Target genes of miR-25-5p were predicted using the TargetScan database. The interaction between miR-25-5p and the 3' untranslated region (3' UTR) of the RAB11B gene (a member of RAS oncogene family) was validated through a dual-luciferase reporter assay. Post-inflammatory hyperpigmentation (PIH) models were established in female C57BL/6J mice (6 - 8 weeks old) and female brown guinea pigs (4 - 6 weeks old) through daily broadband ultraviolet B (UVB) irradiation on the dorsal skin of the mouse ear or shaved dorsal skin of guinea pigs, while untreated mice and untreated dorsal skin areas of guinea pigs served as control groups. During modeling, these experimental animals received intradermal injections of a miR-25-5p agomir or a miR control agomir. Changes in skin pigmentation were observed, and skin tissue samples were harvested for further analysis after modeling. Melanin content in skin tissues was evaluated using Masson-Fontana staining. Expression of RAB11B and tyrosinase (TYR) in skin tissues was determined using immunohistochemical staining and quantitative real-time PCR (qPCR). Primary human melanocytes were isolated from discarded normal foreskin tissues of healthy males after circumcision. Both primary human melanocytes and human MNT1 melanoma cells were transfected with miR-25-5p mimics or miR control mimics. Relative expression levels of miR-25-5p and RAB11B mRNA were quantified by qPCR using the 2 -ΔΔCt calculation method. In MNT1 cells, miR-25-5p and RAB11B were co-overexpressed to assess their effect on the mRNA expression of RAB11B and TYR. Statistical analysis was conducted using t test or one-way analysis of variance followed by Tukey's post hoc test for multiple comparisons. Results:The bioinformatic prediction and dual-luciferase reporter assay confirmed a binding site for miR-25-5p in the 3′ UTR of the RAB11B gene. In both animal models, the treatment with the miR-25-5p agomir significantly reduced local skin pigmentation compared to the control groups; Masson-Fontana staining showed a marked decrease in the density of melanin granules in the epidermis and dermis in the miR-25-5p agomir groups compared with the miR control agomir groups (mice: 0.050 ± 0.005 vs. 0.087 ± 0.008; guinea pigs: 0.067 ± 0.015 vs. 0.110 ± 0.013; both P < 0.05). Immunohistochemical staining revealed significantly lower expression of RAB11B in mouse skin tissues in the miR-25-5p agomir group than in those in the miR control agomir group (both P < 0.05). qPCR revealed significantly lower mRNA expression of RAB11B and TYR in skin tissues of guinea pigs in the miR-25-5p agomir group than in those in the miR control agomir group (both P < 0.05). Similarly, RAB11B mRNA expression significantly decreased in the miR-25-5p mimics group compared with the miR control mimics group in primary human melanocytes and MNT1 cells (both P < 0.05). In human MNT1 melanoma cells, miR-25-5p overexpression could suppress TYR mRNA expression, whereas co-overexpression of miR-25-5p and RAB11B could reverse this suppression. Conclusion:Overexpression of miR-25-5p could alleviate UVB-induced post-inflammatory hyperpigmentation and inhibit melanogenesis, likely by targeted suppression of RAB11B expression.