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Updated: May 21, 2025
Injections of Lipopolysaccharide into Mice to Mimic Entrance of Microbial-derived Products After Intestinal Barrier Breach
Published on: May 2, 2018
Oral administration of antimicrobial peptide MPX can effectively regulate LPS-mediated testicular oxidative stress
Chunling Zhu1,2,3, Chengshui Liao4, Yilin Bai5
1College of Animal Science and Veterinary Medicine, Henan Institute of Science and Technology, Xinxiang, 453003, Henan, China.
Abstract:
Oxidative stress and disruption of blood‒testis barrier permeability are considered key factors in the pathogenesis of testicular inflammation, degeneration, and functional impairment, which play crucial roles in male infertility. Antimicrobial peptides (AMPs) are internationally recognized as some of the most promising alternatives to antibiotics. However, the molecular mechanisms by which AMPs regulate oxidative stress and the blood‒testis barrier in the testis are still poorly understood. In this study, we orally administered 0.5 mg/kg antimicrobial peptide MPX (MPX) to mice for 20 and 40 days and evaluated its effects on Lipopolysaccharide LPS-induced testicular oxidative stress and blood‒testis barrier repair, and elucidateed the pharmacokinetics of MPX in mice. The experiment was divided into six groups, control, LPS, MPX, MPX + LPS, Polymyxin and Polymyxin + LPS, respectively. The results showed that oral administration of MPX effectively increased testicular Glutathione (GSH), Total superoxide dismutase (T-SOD), and Catalase (CAT) levels and reduced Nitric oxide (NO) and Malondialdehyde (MDA) levels in the testes and Lactate dehydrogenase (LDH) levels in serum; these findings were consistent with the oxidative stress parameters in the liver. MPX significantly upregulated the expression of Kelch-like ECH-associated protein 1 (Keap1), Nuclear factor erythroid 2-related factor 2 (Nrf2), and Glutamate cysteine ligase, modifier (GLCM) in the testes while downregulating the expression of Glutamate cysteine ligase, catalytic (GCLC) and Inducible nitric oxide synthase (iNOS), thus exerting a regulatory effect on oxidative stress. MPX also effectively increased sperm count and motility and counteracted the LPS-induced blood‒testis barrier damage, and its molecular mechanism involved upregulating the expression of Slug, which subsequently promoted high expression of Claudin, Occludin, Zonula occludens-1 (ZO-1), N-cadherin, and E-cadherin in the testes. After intragastric administration of FITC-MPX for 30 min, FITC-MPX was mainly distributed in the stomach and thoracic cavity, then showed multi-tissue distribution after 30 min. The fluorescence signal could be detected in the testis 1 h later, which confirmed that MPX had testicular targeting. Moreover, both intraperitoneal and intravenous injection of FITC-MPX also confirmed its testicular targeting ability. In conclusion, this study systematically evaluated the long-term effects of the orally administered antimicrobial peptide MPX on oxidative stress and the blood‒testis barrier in the male reproductive system. This study laid the foundation for the antimicrobial peptide MPX to be used in the treatment of male testicular inflammatory diseases.
Insights
Antimicrobial peptide MPX (MPX) orally administered to mice reduced testicular oxidative stress and repaired the blood-testis barrier, improving sperm health. MPX demonstrated testicular targeting, offering potential for treating male reproductive inflammatory diseases.
Area of Science:
- Reproductive Biology
- Pharmacology
- Biochemistry
Background:
- Oxidative stress and blood-testis barrier disruption are key factors in male infertility.
- Antimicrobial peptides (AMPs) show promise as antibiotic alternatives, but their testicular mechanisms are unclear.
- Understanding AMPs' effects on testicular oxidative stress and barrier integrity is crucial for male reproductive health.
Purpose of the Study:
- To evaluate the effects of orally administered antimicrobial peptide MPX on Lipopolysaccharide (LPS)-induced testicular oxidative stress and blood-testis barrier repair in mice.
- To elucidate the molecular mechanisms underlying MPX's effects on oxidative stress and barrier function.
- To determine the pharmacokinetics and testicular targeting of MPX.
Main Methods:
- Oral administration of MPX (0.5 mg/kg) to mice for 20 and 40 days.
- Assessment of oxidative stress markers (GSH, T-SOD, CAT, NO, MDA, LDH) and protein expression (Keap1, Nrf2, GLCM, GCLC, iNOS, Slug, Claudin, Occludin, ZO-1, N-cadherin, E-cadherin).
- Pharmacokinetic studies using FITC-labeled MPX administered via intragastric, intraperitoneal, and intravenous routes.
Main Results:
- MPX administration increased testicular antioxidant levels (GSH, T-SOD, CAT) and decreased oxidative stress markers (NO, MDA, LDH).
- MPX upregulated key proteins in the Nrf2 pathway (Keap1, Nrf2, GLCM) and downregulated iNOS, indicating regulation of oxidative stress.
- MPX improved sperm count and motility, repaired the blood-testis barrier by upregulating Slug and tight junction proteins (Claudin, Occludin, ZO-1), and demonstrated testicular targeting.
Conclusions:
- Orally administered MPX effectively mitigates testicular oxidative stress and repairs the blood-testis barrier in mice.
- MPX exerts its effects by modulating the Nrf2 signaling pathway and promoting the expression of tight junction proteins.
- MPX exhibits testicular targeting and holds potential for treating male testicular inflammatory diseases.
