Background: Despite prompt and appropriate care, Streptococcus pneumoniae (S. pneumoniae) meningitis remains a key cause of childhood morbidity and mortality. Recently, several studies suggested the possibility of microRNAs (miRNA) involvement in multiple brain and infectious diseases. This study aimed to investigate the expressional changes of brain-enriched miRNAs (124, 134, 9, and 138), and inflammation-related miRNAs (132, 181a, 221, and 222) in the cerebral cortex of acute S. pneumoniae meningitis in postnatal day 25 rats with and without treatment. Methodology: Quantitative polymerase chain reaction (qPCR) was used to measure the expression levels of the tested brain-enriched and inflammation-related miRNAs in the cerebral cortical tissues obtained from acute experimental meningitis rat model induced by intracranial inoculation of S. pneumoniae serotype 3 with and without treatment. Control rats inoculated with saline were also included. Results: Brainenriched miRNAs are significantly downregulated in untreated animals while after treatment with antibiotic and steroid for 24 hours, miR-124 and miR-9 expressions were nearly equal to the control, while miR-134 and miR-138 were significantly upregulated. Inflammation-related miR-132 was significantly downregulated in untreated and treated animals while miRNAs (181a, 221, and 222) were significantly upregulated in untreated and treated animals. Conclusion: Acute S. pneumoniae meningitis leads to significant changes in the cerebral cortical expressions of some brain-enriched and inflammation-related miRNAs. These miRNAs may play a role in the pathogenesis of acute bacterial meningitis.

IntroductionThe pathogenesis of bacterial meningitis due to Streptococcus pneumoniae is still unclear. Despite early treatment with antibiotics, its morbidity and mortality is still high.Material and methodsStreptococcus pneumoniae induced rat meningitis models were taken and divided into 2 groups; control (C) and meningitis (M). Western blot was used to detect toll like receptor 4 (TLR4), tumor necrosis factor α (TNF-α), interleukin 1B (IL1B), nuclear factor κB (NFκB) and real time polymerase chain reaction were used to detect the expression of miR146a, miR132, respectively.ResultsWe found that the expressions of TLR4, TNF-α, IL1B, NFκB were all up-regulated in the acute stage of bacterial meningitis when compared to the control group. While for the post transcription factors, miR146a and miR132, the opposite was observed. They were down-regulated in the meningitis group.ConclusionsmiR146a and miR132 may take part in the pathogenesis of SP bacterial meningitis as well as the TLR4- NFκB- TNF-α/IL1B signal transduction pathway.