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[K. pneumoniea endotoxin induced mice beta-defensin-4 mRNA expression and its signaling transduction]
1Research Unit of Infection and Immunity, School of Basic Medical Sciences, WCUMS, Chengdu 610041, China.
Objective:
To investigate the in vivo effects of Klebsiella pneumoniae endotoxin(LPS) on beta-defensin expression and the relevant signaling transduction pathway.
Methods:
A LPS tolerant mouse C3H/HeJ with a point mutation at Toll-like receptor-4 (TLR4) gene and its wild type strain C3H/HeN were used in this study. C3H/HeJ and C3H/HeN were injected with 4 mg/kg of LPS intraperitoneally. The tracheas, lungs and kidneys of the C3H/HeJ and C3H/HeN were collected respectively at different LPS-treated time points, and the total RNA of each sample was extracted. The expression of mice beta-defensin-3 and/or beta-defensin-4 mRNA in these tissues was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). The sequence of cDNA amplified from the lung of C3H/HeN treated by LPS for 24 h was analyzed. By using western blot, p-I kappa B alpha (phosphorylated I kappa B alpha) and I kappa B alpha of in the lungs of C3H/HeJ and C3H/HeN were detected at different time points after treatment with LPS or without LPS.
Results:
1. beta-defensin-4 mRNA was detected in the lungs of C3H/HeN after 24 h treatment with LPS. In contrast, no signal was determined in C3H/HeJ mice with LPS treatment and the C3H/HeN mice without LPS treatment. 2. Compared with the control, increas of the p-I kappa B alpha was observed in the lungs of C3H/HeN at 4 h after treatment with LPS, while both the p-I kappa B alpha and I kappa B alpha contents showed a tendency to go down at 8 h after treatment and dramatically decreased at 24 h. But there were no changes in the of p-I kappa B alpha and I kappa B alpha content the lungs of C3H/HeJ under the same conditions.
Conclusion:
K. pneumoniea endotoxin could induce the expression of beta-defensin-4 mRNA in the lung of C3H/HeN, and TLR4-mediated NF-kappa B activation signaling pathway may be responsible for this event.
Insights
Klebsiella pneumoniae endotoxin (LPS) induces beta-defensin-4 mRNA expression in mouse lungs via the Toll-like receptor-4 (TLR4) pathway. This indicates TLR4-mediated NF-kappa B activation is crucial for the immune response.
Area of Science:
- Immunology
- Molecular Biology
- Microbiology
Background:
- Beta-defensins are key components of the innate immune system.
- Toll-like receptor-4 (TLR4) plays a critical role in recognizing bacterial endotoxins like LPS.
Purpose of the Study:
- To investigate the in vivo effects of Klebsiella pneumoniae lipopolysaccharide (LPS) on beta-defensin expression.
- To elucidate the signaling pathway involved in LPS-induced beta-defensin expression.
Main Methods:
- Used LPS-tolerant C3H/HeJ (TLR4-mutated) and wild-type C3H/HeN mice.
- Administered LPS intraperitoneally and collected lung, trachea, and kidney tissues.
- Quantified beta-defensin-4 mRNA using RT-PCR.
- Assessed NF-kappa B pathway activation via Western blot analysis of p-I kappa B alpha and I kappa B alpha.
Main Results:
- Beta-defensin-4 mRNA was detected in C3H/HeN mouse lungs 24 hours post-LPS treatment, but not in C3H/HeJ mice.
- LPS treatment increased p-I kappa B alpha in C3H/HeN lungs, indicating NF-kappa B pathway activation.
- No significant changes in p-I kappa B alpha or I kappa B alpha were observed in C3H/HeJ mice.
Conclusions:
- Klebsiella pneumoniae LPS induces beta-defensin-4 mRNA expression in the lungs of wild-type mice.
- The TLR4-mediated NF-kappa B signaling pathway is likely responsible for this induction.