Potential natural immunization against atherosclerosis in hibernating bears

Area of Science:

• Comparative immunology
• Mammalian physiology
• Cardiovascular research

Background:

• Brown bears (Ursus arctos) hibernate for extended periods, experiencing physiological changes like kidney insufficiency and dyslipidemia without developing atherosclerosis or cardiovascular disease (CVD).
• Antibodies against phosphorylcholine (anti-PC) and malondialdehyde (anti-MDA) are linked to reduced atherosclerosis and mortality in humans with kidney issues, possessing anti-inflammatory properties.

Purpose of the Study:

• To investigate the levels of anti-PC and anti-MDA antibodies in brown bears during both active (summer) and hibernating (winter) states.
• To explore the potential role of these antibodies in the bears' resistance to atherosclerosis and CVD during hibernation.

Main Methods:

• Serum samples were collected from 12 free-ranging Swedish brown bears during summer and winter hibernation.
• Enzyme-linked immunosorbent assay (ELISA) was used to quantify IgM, IgG, IgG1/2, and IgA isotypes of anti-PC and anti-MDA antibodies.

Main Results:

• Significantly higher levels of anti-PC antibodies, particularly IgA anti-PC, were observed during winter hibernation compared to the summer active state.
• In contrast, most anti-MDA antibody levels were significantly lower in winter, with IgA anti-MDA being undetectable.
• IgA anti-PC levels showed a striking increase (median 782.3 IQR vs. 100 IQR in summer, p < 0.001).

Conclusions:

• Brown bears exhibit a significant increase in anti-PC antibodies during hibernation, suggesting a natural immunization response potentially linked to microbial exposure.
• This immune response may contribute to the bears' protection against atherosclerosis and cardiovascular disease during the vulnerable hibernation period.
• Findings could offer insights into novel therapeutic strategies for atherosclerosis prevention in humans.