Therapeutic effects of inulin-type oligosaccharides of Morinda officinalis on Streptococcus pneumoniae meningitis in mice

doi:10.12122/j.issn.1673-4254.2025.03.15

Abstract

Abstract:

Objective To investigate the therapeutic effects of inulin-type oligosaccharides of Morinda officinalis (IOMO) in a murine model of Streptococcus pneumoniae meningitis (SPM) and explore its possible mechanisms. Methods A total of 120 male C57BL/6J mice were randomly assigned into Sham, SPM+Saline, SPM+IOMO (25 mg/kg), and SPM+IOMO (50 mg/kg) groups. After modeling, the mice received daily gavage of saline or IOMO at the indicated doses for 7 consecutive days, and the changes in symptom scores and mortality of the mice were monitored. Brain pathology and neuronal injury of the mice were assessed using HE and Nissl staining, and qRT-PCR was performed to detect mRNA levels of the inflammatory mediators. Brain edema and blood-brain barrier (BBB) permeability of the mice were evaluated by measuring brain water content and Evans blue (EB) staining; Western blotting was used to analyze the expressions of BBB-associated proteins, and flow cytometry was employed to detect IFN‑γ expression level in the infiltrating lymphocytes. Open-field test (OFT) and novel object recognition test (NORT) were conducted to assess learning and memory ability of the mice on day 21 after modeling. Results IOMO treatment at 50 mg/kg significantly reduced the symptom scores and mortality rate of SPM mice, alleviated brain damage, and downregulated mRNA levels of IL-6, TNF‑α, IL-1β, IL-18, IFN‑γ, iNOS, NLRP3, ASC, caspase-1 and GSDMD in the brain tissue. IOMO treatment also decreased brain water content and EB leakage, upregulated VE-cadherin and occludin expressions, and suppressed AQP4, iNOS, and IFN‑γ levels of the mice. IOMO-treated mice exhibited improved learning and memory compared with the saline-treated mice on day 21 after SPM modeling. Conclusion IOMO alleviates SPM symptoms, reduces mortality, and mitigates cognitive deficits in mice possibly by suppressing cerebral inflammation and protecting BBB functions.

Key words: inulin-type oligosaccharides of Morinda officinalis, meningitis, Streptococcus pneumoniae, blood-brain barrier, interferon-γ

Zehan LI, Meng LIANG, Gencheng HAN, Xuewu ZHANG. Therapeutic effects of inulin-type oligosaccharides of Morinda officinalis on Streptococcus pneumoniae meningitis in mice[J]. Journal of Southern Medical University, 2025, 45(3): 577-586.

Figures/Tables 10

Fig.1 Schedule of treatment.

Tab.1 Primer sequence used in qRT-PCR

Gene	Primer sequence (5'-3')
18S	F:TTGACGGAAGGGCACCACCAG
	R:GCACCACCACCACGGAATCG
TNF-α	F:CCCTCACACTCAGATCATCTTCT
	R:GCTACGACGTGGGCTACAG
IL-6	F:GATGGATGCTACCAAACTGGA
	R:TCTGAAGGACTCTGGCTTTG
IL-1β	F:TGAAGCAGCTATGGCAACTG
	R:AGGTCAAAGGTTTGGAAGCA
IL-18	F:CCAAATCACTTCCTCTTGGC
	R:GGCCAAAGTTGTCTGATTCC
IFN-γ	F:AAGCGTCATTGAATCACACCTG
	R:TGACCTCAAACTTGGCAATACTC
iNOS	F:GTTCTCAGCCCAACAATACAAGA
	R:GTGGACGGGTCGATGTCAC
NLRP3	F:ATTACCCGCCCGAGAAAGG
	R:TCGCAGCAAAGATCCACACAG
ASC	F:CTTGTCAGGGGATGAACTCAAAA
	R:GCCATACGACTCCAGATAGTAGC
Caspase-1	F:ACAAGGCACGGGACCTATG
	R:TCCCAGTCAGTCCTGGAAATG
GSDMD	F:CCATCGGCCTTTGAGAAAGTG
	R:ACACATGAATAACGGGGTTTCC

Fig.2 IOMO reduces symptom scores (A) and mortality rate (B) of SPM mice (Mean±SD, n=8). *P<0.05, #P<0.05.

Fig.3 HE staining of brain histopathology of the mice (Original magnification: ×1.2, ×14).

Fig.4 Nissl staining of the brain tissue of the mice (×1.2, ×32).

Fig.5 Effects of IOMO on mRNA levels of inflammation-related molecules mRNA levels in the cerebral cortex of SPM mice (Mean±SD, n=4). *P<0.05 vs Sham group, #P<0.05 vs SPM+Saline group.

Fig.6 Effects of IOMO on brain water content and BBB permeability of SPM mice (Mean±SD, n=6). A: Evans blue (EB) staining. B: Statistics of the results of EB staining. C: Statistics of brain water content. *P<0.05 vs Sham group,#P<0.05 vs SPM+Saline group.

Fig.7 Effects of IOMO on BBB permeability-related molecular levels in SPM mice (Mean±SD, n=6). *P<0.05 vs Sham group,#P<0.05 vs SPM+Saline group.

Fig.8 Assessment of IFN-γ levels in the infiltrating lymphocytes (Mean±SD, n=4). *P<0.05 vs Sham group,#P<0.05 vs SPM+Saline group.

Fig.9 IOMO alleviates SPM-induced learning and memory dysfunction in mice (Mean±SD, n=8). A, B: Traveling traces and statistics in open field test (*P<0.05 vs Crossing Training). C: Statistics of the results of new object recognition test (*P<0.05 vs familiar group).

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