Ageing of the carotid body

Abstract

The ageing process is characterized by a decline in several physiological functions resulting in a reduced capability to maintain homeostasis. The lowered homeostatic capacity seems to involve the carotid body (CB), whose role is to modulate ventilation and tissue oxygen supply. It thus plays a prime role in all ageing processes. Ageing causes marked changes in CB morphology. In older animals, it is enlarged and shows a concomitant decrease in the percentage of chemoreceptor tissue, as well as a proliferation of type II cells. The carotid glomitis is present with aggregates of lymphocytes and fibrosis of the lobules. Type I cells are dehydrated, with a profound vacuolization, a shrinking nucleus, and lipofuscin accumulation. With increased age, human CB shows a reduction in the number and volume of mitochondria, fewer synaptic junctions between glomi, along with a reduction in CB content of neurotransmitters, leading to a sort of 'physiological denervation'. Ageing could be interpreted as a cumulative result of oxidative damage to cells, which derives from aerobic metabolism. Moreover, metabolic rate is tightly correlated with life duration; thus a loss in mitochondrial function is one of the prime factors affecting CB ageing processes. The age-related reduction in synaptic junctions might be a self-protective mechanism through which cells buffer themselves against an accumulation of reactive oxygen species. The correlation between hypoxia and the life duration of CB cells remains an open question until how and why cells sense oxygen is understood.

Contribution of adenosine and ATP to the carotid body chemosensory activity in ageing

“…It is generally agreed that ageing leads to an enlargement of CBs, which is concomitant with a decrease in the number of type I cells (for a review see Di Giulio, ). Our results obtained in Fig.…”

“…Ageing can be described as a sum of changes that occur in a living organism that progress to a functional impairment). It has been previously described that the function of the CB declines with age, this being associated with alterations in CB morphology (for a review see Di Giulio, ). In agreement with this, we described here an altered CB ratio of type I/type II cells in old animals, consistent with the decrease in 49.04% in the immunoreactivity for TH (Fig.…”

“…; Pokorsky et al . ; for a review see Di Giulio, ). It was described as an increase in extracellular matrix, a reduction in the number of chemoreceptor cells and a decrease in the mitochondrial volume similar somehow to that observed in chronic hypoxia (Wang & Bisgard, ).…”

Advances in cellular and integrative control of oxygen and carbon dioxide homeostasis

“…() summarizes the present knowledge of the neonatal evolvement of central and peripheral chemoreflexes during the postnatal period (critical period) and its relation to the pathogenesis of sudden infant death syndrome. On the other end of this spectrum, Di Giulio () summarizes the role of the carotid body in the decline of homeostatic capacity with ageing.…”

“…Continuing on a developmental theme, the review by Porzionato et al (2018) summarizes the present knowledge of the neonatal evolvement of central and peripheral chemoreflexes during the postnatal period (critical period) and its relation to the pathogenesis of sudden infant death syndrome. On the other end of this spectrum, Di Giulio (2018) summarizes the role of the carotid body in the decline of homeostatic capacity with ageing. The carotid bodies play an important role as the main oxygen sensor for arterial oxygen homeostasis in the body, but they also coordinate their central input with central chemoreceptor pathways for the maintenance of arterial CO 2 homeostasis.…”