Oxidative Damage and Autophagy in the Human Trabecular Meshwork as Related with Ageing

Abstract

Autophagy is an intracellular lysosomal degradation process induced under stress conditions. Autophagy also plays a major role in ocular patho-physiology. Molecular aging does occur in the trabecular meshwork, the main regulator of aqueous humor outflow, and trabecular meshwork senescence is accompanied by increased oxidative stress. However, the role of autophagy in trabecular meshwork patho-physiology has not yet been examined in vivo in human ocular tissues. The purpose of the herein presented study is to evaluate autophagy occurrence in ex-vivo collected human trabecular meshwork specimens and to evaluate the relationship between autophagy, oxidative stress, and aging in this tissue. Fresh trabecular meshwork specimens were collected from 28 healthy corneal donors devoid of ocular pathologies and oxidative DNA damage, and LC3 and p62 protein expression analyzed. In a subset of 10 subjects, further to trabecular meshwork proteins, the amounts of cathepesin L and ubiquitin was analyzed by antibody microarray in aqueous humor. Obtained results demonstrate that autophagy activation, measured by LC3II/I ratio, is related with. oxidative damage occurrence during aging in human trabecular meshwork. The expression of autophagy marker p62 was lower in subjects older than 60 years as compared to younger subjects. These findings reflect the occurrence of an agedependent increase in the autophagy as occurring in the trabecular meshwork. Furthermore, we showed that aging promotes trabecular-meshwork senescence due to increased oxidative stress paralleled by autophagy increase. Indeed, both oxidative DNA damage and autophagy were more abundant in subjects older than 60 years. These findings shed new light on the role of oxidative damage and autophagy during trabecular-meshwork aging.

Autophagic dysregulation in glaucomatous trabecular meshwork cells

“…Interestingly, a recent work by Pulliero et al has reported a parallel increase in oxidative damage and increase LC3-II/LC3-I protein levels in TM tissue with aging [37]. These results do not contradict, rather complement our findings here.…”

The autophagic lysosomal system in outflow pathway physiology and pathophysiology

“…A recent work by Pulliero et al has reported the occurrence of an age dependent increase in autophagy in the TM tissue (Pulliero et al, 2014). Furthermore, they showed that aging promotes TM senescence due to increased oxidative stress paralleled by autophagy increase.…”

Autophagy in glaucoma: Crosstalk with apoptosis and its implications

“…This study suggests that the activation of autophagy by stretching the TM cells is a physiological response that TM cells use to cope with mechanical forces [65]. Pulliero et al [66] lately used fresh TM specimens from 28 healthy human donor eyes and demonstrated that the SQSTM 1/p62 protein levels of subjects over 60 years of age were lower than those of the younger subjects, which suggests that autophagy in human TM is upregulated with age. The discrepancy between Porter's [64] and Pullieroet's [66] studies might reflect the difference in the autophagy activity either in different animal (including human) species, or under different stimulative circumstance (oxidative stimulation vs. normal physiological condition).…”

“…Pulliero et al [66] lately used fresh TM specimens from 28 healthy human donor eyes and demonstrated that the SQSTM 1/p62 protein levels of subjects over 60 years of age were lower than those of the younger subjects, which suggests that autophagy in human TM is upregulated with age. The discrepancy between Porter's [64] and Pullieroet's [66] studies might reflect the difference in the autophagy activity either in different animal (including human) species, or under different stimulative circumstance (oxidative stimulation vs. normal physiological condition). The alteration in the autophagy activity in response to different stimuli needs further investigation, especially in the glaucoma patients.…”