Abstract
All retinal disorders, regardless of their aetiology, involve the activation of oxidative stress and apoptosis pathways. The administration of neuroprotective factors is crucial in all phases of the pathology, even when vision has been completely lost. The retina is one of the most susceptible tissues to reactive oxygen species damage. On the other hand, proper development and functioning of the retina requires a precise balance between the processes of proliferation, differentiation and programmed cell death. The life-or-death decision seems to be the result of a complex balance between pro- and anti-apoptotic signals. It has been recently shown the efficacy of natural products to slow retinal degenerative process through different pathways. In this review, we assess the neuroprotective effect of two compounds used in the ancient pharmacopoeia. On one hand, it has been demonstrated that administration of the saffron constituent safranal to P23H rats, an animal model of retinitis pigmentosa, preserves photoreceptor morphology and number, the capillary network and the visual response. On the other hand, it has been shown that systemic administration of tauroursodeoxycholic acid (TUDCA), the major component of bear bile, to P23H rats preserves cone and rod structure and function, together with their contact with postsynaptic neurons. The neuroprotective effects of safranal and TUDCA make these compounds potentially useful for therapeutic applications in retinal degenerative diseases.
Highlights
The retina is the light-sensitive tissue that lines the inner surface of the eye and is in charge of the first steps of visual processing
The second approach is not concerned as much with the causes of the diseases as it is with ways to prevent cell death, such as the administration of anti-apoptotic, anti-inflammatory and neurotrophic compounds
In P23H rat retinas, microglia density increased in the ganglion cell layer (GCL), IPL and OPL, microglial cells appears in the subretinal space (SS), and a great deal of microglial cells were labeled with anti-MHC-II, a marker of microglia activation (Figure 2)
Summary
The retina is the light-sensitive tissue that lines the inner surface of the eye and is in charge of the first steps of visual processing. In human samples and animal models of retinitis pigmentosa, the morphological characteristics of apoptosis have been described [26,27,28], even though more recent evidences suggest that photoreceptor cell death may result primarily from non-apoptotic mechanisms [23,24,25]. The majority of RP-causing mutations in the RHO gene, including P23H, cause misfolding and retention of rhodopsin in the endoplasmic reticulum [32] These studies suggest that the mechanism of RP involves a cellular stress response [33], the final common pathway being programmed during photoreceptor cell death [34]. The administration of neuroprotective factors, which slow retinal degeneration, may be crucial in all phases of the pathology, even when vision has been completely lost
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