OBJECTIVE To investigate the correlation between the expression of microRNA-455-5p (MiR-455-5p) and monocyte chemoattractant protein-1 (MCP-1) in serum and mitochondrial function as well as prognosis outcome in neonatal late-onset sepsis.

METHODS Eighty neonates with late-onset sepsis admitted to the Neonatal Intensive Care Unit of Beijing Children′s Hospital, Capital Medical University (Baoding Hospital) from 2021 to 2023 were selected as the septicemia group, while 80 healthy neonates during the same period were recruited as the control group. Inflammatory markers were compared between the two groups through biochemical analysis. The expression levels of MiR-455-5p and MCP-1 mRNA were detected by quantitative real-time reverse transcription PCR (qRT-PCR). Mitochondrial function was compared between the two groups. The impact of MiR-455-5p and MCP-1 expression on prognosis of children was analyzed with Kaplan-Meier survival curves.

RESULTS The septicemia group showed elevated white blood cell count (WBC), C-reactive protein (CRP), procalcitonin (PCT) and neutrophil-to-lymphocyte ratio (NLR) compared to the control group (P < 0.05). The expression levels of MiR-455-5p and MCP-1 mRNA was higher in the septicemia group than in the control group (P < 0.05). Mitochondrial membrane potential was lower, and ATP production was reduced in the septicemia group compared to the control group (P < 0.05). Children with high expression levels of MiR-455-5p and MCP-1 had a higher probability of poor prognosis than those with low expression (P < 0.001).

CONCLUSIONS In neonatal late-onset sepsis, high expression levels of MiR-455-5p and MCP-1 are closely associated with disease severity and poor prognosis. MiR-455-5p and MCP-1 exacerbate the condition by intensifying inflammatory responses, impairing immune cell function and mitochondrial dysfunction, thereby affecting cellular energy metabolism and survival.