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Photoperiodic adjustments in immune function protect Siberian hamsters from lethal endotoxemia
Brian J Prendergast1, Andrew K Hotchkiss, Staci D Bilbo
1Department of Psychology and Neuroscience, The Ohio State University, Columbus, OH 43210, USA. prendergast@psy.ohio-state.edu
Journal of Biological Rhythms
|February 6, 2003
Summary
Short days enhance immune survival in Siberian hamsters, improving resistance to endotoxin (lipopolysaccharide). This adaptation, particularly in males, involves reduced inflammatory cytokine production, mitigating septic shock effects.
Area of Science:
- Immunology
- Endocrinology
- Mammalian Physiology
Background:
- Seasonal changes in photoperiod influence mammalian immune function.
- Siberian hamsters exhibit photoperiod-dependent alterations in neuroendocrine, reproductive, and immune systems.
- The integration of these immune changes into host defense against pathogens remains unclear.
Purpose of the Study:
- To investigate if short-day induced immune changes affect the pathogenesis and survival of endotoxemia.
- To test the hypothesis that altered immune function in short-day adapted hamsters impacts endotoxin lethality.
Main Methods:
- Siberian hamsters (male and female) were exposed to either long or short days.
- After 6-8 weeks, hamsters received intraperitoneal injections of bacterial lipopolysaccharide (LPS) at varying doses.
- Survival rates were monitored for 96 hours; in vitro and in vivo cytokine (TNF-alpha) production was assessed.
Main Results:
- Short-day exposure significantly improved survival in male hamsters challenged with LPS (10-25 mg/kg) and in females (50 mg/kg).
- The median lethal dose (LD50) of LPS increased by ~90% in males and ~35% in females adapted to short days.
- Short-day hamsters exhibited lower in vitro tumor necrosis factor-alpha (TNF-alpha) production and lower circulating TNF-alpha levels post-LPS challenge.
Conclusions:
- Adaptation to short photoperiods enhances hamster survival during endotoxemia.
- Reduced inflammatory cytokine responses (TNF-alpha) to lipopolysaccharide in short-day conditions appear to mediate this increased resistance.
- Seasonal immune adaptations play a crucial role in the host's ability to withstand immune challenges like septic shock.