Biology subjects

Sanchez, K. K.

Publications and source records attributed to Sanchez, K. K..

3 recordsLinked to original sources

bioRxiv2023

Age-dependent roles of cardiac remodeling in sepsis defense and pathogenesis

Disease tolerance is a defense strategy essential for survival of infections, limiting physiological damage without killing the pathogen. The disease course and pathology a pathogen may cause can change over the lifespan of a host due to the structural and functional physiological changes that accumulate with age. Since successful disease tolerance responses require the host to engage mechanisms that are compatible with the disease course and pathology caused by an infection, we predicted that this defense strategy would change with age. Animals infected with a lethal dose 50 (LD50) of a pathogen often display distinct health and sickness trajectories due to differences in disease tolerance, and thus can be used to delineate tolerance mechanisms. Using a polymicrobial sepsis model, we found that despite having the same LD50, old and young susceptible mice exhibited distinct disease courses. Young survivors employed a cardioprotective mechanism via FoxO1-mediated regulation of the ubiquitin-proteosome system that was necessary for survival and protection from cardiomegaly. This same mechanism was a driver of sepsis pathogenesis in aged hosts, causing catabolic remodeling of the heart and death. Our findings have implications for the tailoring of therapy to the age of an infected individual and suggest that disease tolerance alleles may exhibit antagonistic pleiotropy.

immunology↗

bioRxiv2022

CD4+ T cells regulate sickness-induced anorexia and fat wasting during a chronic parasitic infection

Catabolic responses of lean and fat energy stores are a component of the host response to infection. Cachexia is an extreme catabolic state characterized by unintentional weight loss and muscle loss, that can include fat loss. Whether cachexia plays any role in host defense or is a maladaptive consequence of host-pathogen interactions remains unknown. Traditionally studies have focused on understanding how inflammatory mediators and cells of the innate immune system contribute to the pathogenesis of cachexia and the depletion of energy stores. The cells of the adaptive immune system that regulate infection-induced cachexia remain elusive. In the present study, we examined the role of the adaptive immune response in cachexia pathogenesis using a murine model of the chronic parasitic infection Trypanosoma brucei, the causative agent of sleeping sickness. We found that the cachectic response occurs in two phases with the first stage occurring early in the infection and involved a loss of body fat mass associated with anorexia, and the second stage occurring later in the infection and involved a sustained loss of fat mass that was accompanied by lean mass wasting. CD4+ T cells were necessary for the development of the sickness-induced anorexic response during stage 1 of the infection, which led to adipose triglyceride lipase dependent lipolysis in adipocytes and the resulting fat wasting. Adipose tissue wasting had no impact on host resistance defenses or survival of infection, both of which were antibody-mediated and independent ofCD4+ T cell responses. Our work reveals a new mechanism for infection induced cachexia involving CD4+ T cell regulation of host feeding behavior and an unexpected decoupling of adaptive immune mediated resistance from the cachectic response during infection.

immunology↗

bioRxiv2020

Leptin signaling regulates physiological damage and host-pathogen cooperation

To combat infections, hosts employ a combination of antagonistic and cooperative defense strategies. The former refers to pathogen killing mediated by resistance mechanisms, while the latter refers to physiological defense mechanisms that promote host health during infection independent of pathogen killing, leading to an apparent cooperation between the host and the pathogen. Previous work has shown that leptin, a pleiotropic hormone that plays a central role in regulating appetite and energy metabolism, is indispensable for resistance mechanisms, while a role for leptin signaling in cooperative host-pathogen interactions remains unknown. Using a mouse model of Yersinia pseudotuberculosis (Yptb) infection, the causative agent of Far East scarlet-like fever, we unexpectedly found that genetic inhibition of leptin signaling conferred protection from Yptb infection due to increased host-pathogen cooperation rather than greater resistance defenses. The protection against Yptb infection was not due to differences in food consumption, lipolysis or fat mass. Furthermore, we found that the survival advantage was associated with increased liver damage and dysfunction. Our work reveals an additional level of complexity for the role of leptin in infection defense and suggests that in some contexts, in addition to tolerating the pathogen, tolerating organ damage and dysfunction is more beneficial for survival than preventing the damage.

immunology↗