Related Experiment Video
Updated: Jan 7, 2026
Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
Differential Antipyretic Effects of Toll-Like Receptor 4 Signal Inhibitors in Male Rats
Tuğçe Nomenoğlu1, İbrahim Mert Yüksel1, Soner Mamuk1
1Department of Medical Pharmacology, Faculty of Medicine, Ankara University, Ankara, Turkey.
Background:
Pattern recognition receptors (PRR) are responsible for detecting pathogens and danger signals in organisms. Toll-like receptor 4 (TLR4) recognizes lipopolysaccharide (LPS) and some danger-associated molecular patterns (DAMPs). Activation of this receptor initiates sickness behavior. Fever is a hallmark of this process.
Objectives:
We hypothesized that TLR4 signal inhibitors may have antipyretic activity. We evaluated the effect of TLR4 signal inhibitors on LPS or carrageenan-induced fever in male Wistar rats.
Methods:
Core body temperature was measured via telemetric implants. Fever was induced by injection of LPS (E. coli O111:B4, 250 μg/kg, sc) or carrageenan (50 mg/kg, sc). For TLR4 signal inhibition, LPS from Rhodobacter sphaeroides (LPS-RS), IAXO-102, or naltrexone was used. Intracardiac blood samples were collected for measurement of interleukin-6 (IL-6), an endogenous pyrogen cytokine in plasma, by ELISA during the initial phase of LPS-induced fever.
Results:
LPS-RS pretreatment (25 or 100 μg/kg, sc) did not inhibit LPS-induced fever and plasma IL-6 elevation. Other alternative TLR4 signal inhibitors, such as IAXO-102 (3 mg/kg, sc) or naltrexone (10 mg/kg, sc), also failed to abolish LPS-induced fever. An intriguing finding is that LPS-RS or naltrexone inhibited the fever caused by carrageenan.
Conclusion:
Data show that TLR4 signal inhibitors have differential antipyretic activity on fever suggesting that some alternative or complementary mechanisms might be operational for LPS-induced fever. Data also suggest that TLR4 signal inhibitors may be an alternative as a possible treatment option for DAMP-mediated clinical pathologies.
Insights
Toll-like receptor 4 (TLR4) inhibitors showed varied effects on fever. While ineffective against lipopolysaccharide (LPS)-induced fever, some inhibitors successfully reduced carrageenan-induced fever, suggesting differential mechanisms.
Area of Science:
- Immunology
- Pharmacology
- Physiology
Background:
- Pattern recognition receptors (PRR) detect pathogens and danger signals.
- Toll-like receptor 4 (TLR4) recognizes lipopolysaccharide (LPS) and danger-associated molecular patterns (DAMPs), initiating sickness behavior and fever.
Purpose of the Study:
- To investigate the potential antipyretic activity of TLR4 signal inhibitors.
- To evaluate the efficacy of TLR4 inhibitors in reducing LPS or carrageenan-induced fever in rats.
Main Methods:
- Core body temperature was monitored using telemetric implants in male Wistar rats.
- Fever was induced via subcutaneous injection of LPS or carrageenan.
- TLR4 signal inhibition was achieved using LPS from Rhodobacter sphaeroides (LPS-RS), IAXO-102, or naltrexone.
- Plasma levels of interleukin-6 (IL-6) were measured via ELISA.
Main Results:
- LPS-RS, IAXO-102, and naltrexone did not inhibit LPS-induced fever or associated IL-6 elevation.
- Interestingly, LPS-RS and naltrexone demonstrated inhibitory effects on carrageenan-induced fever.
Conclusions:
- TLR4 signal inhibitors exhibit differential antipyretic effects, indicating alternative mechanisms for LPS-induced fever.
- TLR4 inhibitors may offer potential therapeutic options for DAMP-mediated clinical conditions.
