Serum Proteins Infer Molecular Protection Against Inflammation in Weddell Seal (Leptonychotes weddellii) Blood

Weddell seals ( Leptonychotes weddellii) are elite divers able to dive up to 900 meters deep and remain submerged for over 90 minutes. Weddell seals have a dramatic dive response to allow for longer, deeper dives including intense bradycardia and constriction of blood vessels, especially those supplying peripheral or visceral organs. Vasoconstriction, hypo-perfusion and subsequent re-oxygenation upon surfacing is known to induce tissue injury in terrestrial mammals via inflammation. Previous work interrogating the Weddell seal’s innate immune system suggested a component in the seal’s blood serum that protects against inflammation. We are using a mouse macrophage (RAW 264.7) cell model to characterize components of the seal’s blood that are anti-inflammatory to lipopolysaccharide (LPS). When exposed to 10 ng/mL LPS, RAW cells supplemented with deproteinated serum from adult Weddell seals lose their protection against inflammation, having 11-fold greater induction of interleukin-6 (IL-6) mRNA expression after a 6-h exposure compared to RAW cells supplemented with intact seal serum (T=3.29, p=0.01). To determine whether anti-inflammatory capacity of serum is innately present in Weddell seals or whether it is acquired in conjunction with development of diving capacity, we compared the protective effects of adult Weddell seal serum against serum from Weddell seal pups collected at approximately their age of weaning, when they had begun diving activities but do not yet dive deep. Following exposure to 10 ng/mL LPS, IL-6 expression was 69% lower in RAW cells supplemented with serum from adult seals compared to those supplemented with serum from pups (T=8.41, p=0.002), suggesting that ontogeny or diving behavior contributes to the development of anti-inflammatory serum. Analysis of adult (n=12) and pup (n=11) serum proteomes revealed a single protein, colony stimulating factor 2 receptor subunit beta (CSF2RB), with a 24-fold higher abundance in adults (P FDR <0.0001). CSF2RB is a pleiotropic cell surface receptor subunit with known functions in innate immunity, erythropoiesis, as well as tissue protection. Therefore, we hypothesize that it plays a role in the anti-inflammatory protection observed in adult seals. Defining the mechanism of action for this protein in seal serum could identify a protective adaptation that facilitates deep and long dives. In a broader context, lessons learned from an extreme diving mammals may identify anti-inflammatory strategies with new clinical relevance. NSF #1921491; #1853326; #2337400. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.