Horses suggested as a useful model for studying asthma in the elderly

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Researchers say the main strengths of a horse model for studying age-related asthma were the natural occurrence of the disease and the long lifespan of the animals.
Researchers say the main strengths of a horse model for studying age-related asthma were the natural occurrence of the disease and the long lifespan of the animals.

Horses could be a useful model for studying asthma in older people, according to researchers.

They cited similarities between aged-related asthma in humans and severe asthma in horses.

Michela Bullone and Jean-Pierre Lavoie, writing in the International Journal of Molecular Sciences, said aging was associated with a dysregulation of the immune system, leading to a general pro-inflammatory state.

It is a process named inflamm-aging – aging related to a chronic state of inflammation.

Oxidative stress is known to have an important role in aging and in regulating immune responses, probably playing a role in the development of age-related diseases.

The function of the respiratory system declines with age, with asthma tending to be worse in older asthmatics than in younger patients.

Bullone and Jean-Pierre Lavoie, in their review, traversed age-related changes affecting the immune system, respiratory structure and function that could contribute to asthma occurrence in the elderly.

They suggested that naturally occurring equine asthma could be a valuable model for studying the importance of oxidative stress, chronic inflammation, and gradual deterioration of the immune system brought on by natural age advancement.

Severe equine asthma, also known as heaves, recurrent airway obstruction (RAO), or summer-pasture associated obstructive pulmonary disease (SPAOPD) is a spontaneously occurring disease of horses and is already a recognized model for human asthma, the pair said.

In its severe form, horses experience episodes of labored breathing at rest triggered by hay dust antigens. With no infection, it is reversible with bronchodilators.

The occurrence of severe equine asthma is determined by the interplay of genetics and environmental factors, they said, appearing clinically only in adult and geriatric horses.

“Whether its subclinical development starts early/earlier in the horse’s life has still to be established.

“What has been shown is that even occasional respiratory insults (as those commonly observed during mild asthma episodes or during viral respiratory infections) increase the risk of severe equine asthma occurrence 7 to 10 fold in horses.

“Nevertheless, a definitive causative relationship has not been established for either of these factors.

“A study has shown how aging also represents a risk factor for the development of severe equine asthma in horses.

Equine asthma characteristics. Oxidative stress plays a role in both mild and severe forms of equine asthma.
Equine asthma characteristics. Oxidative stress plays a role in both mild and severe forms of equine asthma. Image: Bullone and Lavoie, doi: 10.3390/ijms18122612

“While animals that are older than five years are already five times more at risk of developing asthma as compared to younger animals, in horses aged over 15 years the risk increases up to 18 times more.”

The reasons are not clear.

Evidence also existed supporting the occurrence of inflamm-aging in horses, they said.

“As severe equine asthma mainly affects adult and geriatric horses, the contribution of immunosenescence (that’s aged-related deterioration of the immune system), inflamm-aging, and age-related oxidative stress to its development should not been underestimated.”

Severe equine asthma represented a suitable model for studying the contribution of oxidative stress and inflammatory-related aging to asthma development in the elderly, and its possible implication in treatment response, they suggested.

Bullone and Lavoie said the main strengths of a horse model were the natural occurrence of the disease and the long lifespan of the animals.

“Horses are a long-lived species when compared with other asthma models (i.e., rodents) with a mean lifespan of 25 years, estimated to be equivalent to 71 year of age in people, which can extend up to 40 years in some subjects.

“On the other hand, these features of the disease could represent drawbacks if we aim at studying the immunity mechanisms that are leading to the occurrence of the disease, as currently, there are no means to predict animals that will eventually develop the disease.

“Efforts should be directed toward a thorough characterization of immunity dysfunctions or inflammatory pathways/endotypes in mild equine asthma, and their relationship with the outcome of the disease (possible evolution toward severe equine asthma or complete disease remission).”

Bullone is with the Department of Clinical and Biological Sciences at the University of Turin, Italy, and Lavoie is with the Department of Clinical Sciences, within the Faculty of Veterinary Medicine at the University of Montreal in Canada.

The Contribution of Oxidative Stress and Inflamm-Aging in Human and Equine Asthma
Michela Bullone and Jean-Pierre Lavoie
Int. J. Mol. Sci. 2017, 18(12), 2612; doi: 10.3390/ijms18122612
The study, published under a Creative Commons License, can be read here

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